Biomedical sciences Flashcards
What is anatomy?
Study of internal + external structures of the body, and the physical relationship among body parts
What is physiology?
Study of the functions and activities of structures of the body (cells, tissues and organs) and of the physical and chemical changes involved
What are the 3 types of anatomy?
Regional
Systems
Surface
What is regional anatomy?
How different body structures work together in a particular region of the human body
What is systems anatomy?
The anatomy of a body system e.g.
cardiovascular system in relation to the head and neck
What is surface anatomy?
The study of anatomical landmarks that can be identified by observing the surface of the body in a particular area
What is pathology?
The study and diagnosis of a disease
What is pathogenesis?
The specific cause of a disease at the cell or tissue level
What is pathophysiology?
The abnormalities of a disease (the pathogenesis) – how this affects normal physiology, often causing illness
What is embryology?
The science of the development of an embryo from the fertilisation of the ovum to the foetal stage
Give 3 reasons why anatomical terms are used
- Form of standardisation across health professionals
- Describes anatomy so it’s easy to understand no matter direction/ position of organism and limbs
- Avoids confusion as organisms can rake on dif positions, changing relative placement
What is the standard position of reference?
S- standing upright
P- palms facing forward
A-arms straight
F- facing forward
F- feet together + parallel
T- toes pointing forward
What do directional terms allow?
Description of an anatomical position by comparing location relative to other structures / within the body
What are the 7 main directional terms?
Anterior (ventral) VS posterior (dorsal)
Superior (cranial) VS interior (caudal)
Medial VS lateral
Proximal VS distal
Deep VS superficial
Bilateral VS unilateral
Ipsilateral VS contralateral
What is anterior / posterior?
Anterior- towards the front
Posterior- towards the back
What is superior / inferior?
Superior- upper, towards the head
Inferior- lower, away from the head
What is medial / lateral?
Medial- towards the midline
Lateral- away from the midline
What is proximal / distal?
Proximal- toward/nearest the trunk (point of origin)
Distal- away from/farthest from the trunk (point of origin)
What is deep / superficial?
Deep- farther from the surface of the body
Superficial- closer to the surface of the body
What is unilateral / bilateral?
Unilateral- on one side of the body
Bilateral- on both sides of the body
What is ipsilateral / contralateral?
Ipsilateral- same side of the body
Contralateral- opposite side of the body
What are anatomical planes?
Sections/slices of the body or organs
What are the 3 types of anatomical planes?
Frontal (coronal)
Sagittal
Transverse
How does the frontal/coronal plane divide the body or organ?
Anterior and posterior
How does the sagittal plane divide the body or organ?
Left and right
How does the transverse plane divide the body or organ?
Superior and inferior
What are the 9 levels of organisation in the human body?
Atoms
Molecules
Macromolecule
Organelles
Cells
Tissues
Organs
Organ Systems
Organism
What are cells?
Basic living units
Smallest subdivision able to carry out life processes
Contains organelles
Specialised for specific physiological roles
How do different types of cells exist?
Cell differentiation from stem cells in embryonic development
What are specialised cells?
Cells adapted to specific functions
What are the 3 types of stem cells?
Totipotent embryonic
Pluripotent embryonic
Multipotent (still have as adults)
How are specialised tissues formed? Give an example
Specialised cells work together
Neuron -> nervous tissue -> brain -> nervous system
What are organelles?
Structure with a specific cell function
What does the cell membrane do?
Separates and transports molecules in/out of the cell
What is the cytoskeleton?
Microtubules + microfilaments + centrosome for support and movement
What is the cytoplasm?
Jelly like fluid containing organelles + dissolved molecules
What is the nucleus?
Contains DNA, arranged in chromosomes
Contains the nucleolus (where ribosomes made, helps make proteins)
Membrane bound by nuclear envelope with small pores
What do mitochondria do?
They metabolise glucose in the presence of oxygen to produce ATP for energy: Glucose + Oxygen → Carbon Dioxide + Water + ATP
Also contains small amount of DNA
What is the rough endoplasmic reticulum?
Site of protein folding after being synthesised on
ribosomes
What is the smooth endoplasmic reticulum?
Site of lipid synthesis
What is the golgi body?
Where proteins are sorted + transported to other parts of the cell/outside the cell
What do lysosomes do?
Break down old organelles
What is the cell membrane made of?
The phospholipid bilayer
What is the cell membrane?
Barrier around all cells, separates outside and inside of the cell
Controls movement of substances in/out of cell
Keeps atoms + molecules at optimum concentrations in/out of cell, protects internal envrionement
What is the phospholipid bilayer made of?
2 layers of phospho-lipid molecules
Describe phosphate heads
Hydrophilic (attracted to water) so face outward towards cytoplasm or extracellular fluid
Describe lipid tail
Hydrophobic (repelled by water) so face inward to eachother
How permeable are cell membranes?
Selectively permeable
What are cell membranes permeable to?
Gases cross rapidly (eg: O2)
Molecules made of lipid cross rapidly (eg: testosterone)
Small polar (partly charged) molecules cross slowly (eg: water)
What are cell membranes impermeable to?
Large polar molecules as hydrophilic, repelled by hydrophobic lipids (eg: glucose)
Ions (charged) repelled by hydrophobic lipids (eg: Na+)
What do membrane proteins do?
Control transport of ions + larger molecules in/out of cells
Allow cell-cell communication
What are the 4 main types of membrane proteins?
Channel protein
Carrier protein
Glycoprotein
Receptor protein
How does cholesterol (a lipid) help the cell membrane?
Provides rigidity/support
What are the 3 types of passive transport?
Diffusion
Facilitated diffusion
Osmosis
What is facilitated diffusion?
Movement of larger/ charged molecules using
membrane proteins
What is osmosis?
The passive movement of water molecules from a region of higher concentration (more dilute) to a region of lower concentration (more concentrated) across the partially/selectively permeable phospholipid bilayer of cell membranes
Why does osmosis matter in the human body?
Important to keep ion + water concentrations equal (isotonic) inside and outside the cell
What happens if the solution outside cells becomes hypotonic (watery)?
Water will diffuse by osmosis into the cells
What happens if the solution outside cells becomes hypertonic (less watery)?
Water will diffuse by osmosis out of the cells
What is active transport?
Movement of materials through the cell membrane from low to high concentration, against the concentration gradient- requires energy ie: ATP
What are 2 examples of important cell membrane proteins?
Na+K+ ATPase pump
CFTR- channel protein in cystic fibrosis
What is the NA+K+ ATPase pump?
Protein found in all cell membranes
Carries out active transport so uses ATP
Pumps 3Na+ out, 2K+ in to maintain correct ionic balance in/out of cell
What is cystic fibrosis caused by?
Defect in a single transmembrane protein: cystic fibrosis transmembrane conductance regulator (CFTR)
CFTR is an ion channel membrane protein that transports Cl- ions out of the cell, and defect prevents movement of chloride ions out
Water moves in by osmosis, mucus on cell
surface dries out, builds up
What is an ion?
Atom/molecule with a net +/- electrical charge
How are ions formed?
By substances in our diet called electrolytes
Electrolytes can dissolve or dissociate in our body water into ionic forms
eg: NaCl dissolves into Na+ and Cl- ions
Which ions are at high concentration in extracellular fluid?
Na+
Cl-
Which ion is at high concentration in intracellular fluid?
K+
Which ions are ion channel proteins specific for?
K+
Na+
Cl-
Ca2+
What do ion channel proteins do?
Transports ions across cell membranes, critical for many cellular functions eg: electrical excitability, regulation of bodily fluids
What are the 4 types of tissue in the human body?
Epithelial
Nervous
Muscle
Connective
What are the 3 functions of epithelial tissue?
Forms the skin to cover the body, portects against germs
Forms serous membranes that line body cavities
Forms mucous membranes that line the tracts
What are the 4 different types of epithelial tissue?
Simple squamous epithelium
Stratified squamous epithelium
Simple columnar epithelium
Pseudostratified columnar epithelium
Where can simple squamous epithelium be found?
Air sacs of the lung
Where can stratified squamous epithelium be found?
Vocal cords
Mouth
Vestibule of nasal cavity
Where can simple columnar epithelium be found?
Small bronchioles of lungs
Where can psuedostratified columnar epithelium be found?
Throughout respiratory tract (nasal cavity to bronchi)
Where is nervous tissue located?
CNS (central nervous system)
PNS (peripheral nervous system)
What is the function of nervous tissue?
Transmits information
What types of cells are found in nervous tissue?
Neuron
Glial cells
What are the 3 types of muscle tissue?
Skeletal muscle
Cardiac muscle
Smooth muscle
Describe skeletal muscle
Voluntary contractions
Striated appearance, attached to skeleton
Produces heat
Describe cardiac muscle
Involuntary contractions
Striated
Heart contractions
Describe smooth muscle
Involuntary contractions
Non-striated
Blood vessels, gastrointestinal tract, bladder
What are 2 important skeletal muscles in SLT?
Facial muscles
Muscles of mastication
Where is connective tissue located?
Component of all major tissues
Most abundant type of tissue in the body
What are 4 functions of connective tissue?
Supportive tissue
Part of musculoskeletal system (bone, cartilage, tendons, ligaments)
Fat storage and deposition (adipose tissue)
Some immune functions
What is the general structure of connective tissue?
Consists of cells called fibroblasts (areolar tissue)- secretes fibres (eg: collagen, elastic fibres) and matrix to form an extracellular material surrounding itself
Extracellular matrix can be solid/ gel-like / liquid -> physical consistency depends on the mechanical support needed
Minimal blood supply- depends on tissue fluid for nourishment and waste removal
What are the 6 types of connective tissue?
Dense connective tissue
Adipose tissue
Areolar tissue
Bone
Cartilage
Blood
What is dense connective tissue?
Strong + dense + organised to form ligaments, tendons, capsules, fascia
What are bone cells surrounded by?
Matrix containing calcium hydroxyapatite
What are the 2 types of bone tissue?
Compact bone (cortical bone)
Spongy bone (trabecular or cancellous bone)
Describe compact bone
Outer layer of bones
Dense + hard
Describe spongy bone?
Inner area of bones has trabeculae (spikes) and airspaces
Maximum strength, minimum weight
Spaces filled with red/yellow bone marrow
What are the 3 properties of cartilage?
Great compressive and tensile strength
Not as strong as bone but more resistant to compression, more elastic
Smooth – covering for bones to reduce friction
What are the 3 basic types of cartilage?
Hyaline
Elastic
Fibrocartilage
Describe hyaline cartilage
Smooth, glassy, blue/white, widely distributed,
covers bones at the ends, gliding, low friction
Synovial joints (hinge joints)
Describe elastic cartilage
Many elastin fibres, lots of flexibility
Describe fibrocartilage
Collagen fibres cushion between bones, vertebral disks
What are the 2 types of joints?
Synovial
Non-synovial
Describe synovial joints
Freely mobile, surfaces glide as covered with hyaline
Innervated- nerves detect position + movement
Describe non-synovial joints
Slightly moveable joints or immovable joints
What are some examples of connective tissue prominent in the head and neck?
Bones of the face, cranium and inner ear, skull,
vertebrae
Cartilage - nose, trachea, epiglottis, ears
Fascia around nerves, muscles and blood vessels
Adipose tissue - cheek fat pads
Tendons, ligaments for movement of the jaw at the
temporomandibular joint
What is homeostasis?
Keeping the body’s precise internal conditions within a set range, despite internal or external environmental fluctuations, using negative feedback mechanisms
What do vital signs provide?
Valuable insight into a patient’s condition
- how they respond to medical treatment
- if they’re deteriorating
What are the 2 ways in which the body maintains homeostasis?
Neural control
Endocrine control
What are the 2 structures involved in the neural control to maintain homeostasis?
Brainstem
Hypothalamus
What does the brain stem control regarding homeostasis?
Vitals
- breathing
- heart rate
- blood pressure
- has sensors for blood O2, CO2, pH
What does the hypothalamus control regarding homeostasis?
Temperature
Fluid balance
Overall regulation of many hormones
What are 4 glands and their hormones involved in endocrine control regarding homeostasis?
Pituitary gland → growth hormone
Adrenal gland → aldosterone
Pancreas → insulin + glucagon
Thyroid → thyroid hormone + calcitonin
What is a negative feedback loop/system?
If the value of the regulated variable is disturbed, system functions to restore it toward set point
What are 4 examples of homeostatic mechanisms?
Thermoregulation (maintains body temperature)
Chemoregulation (maintains breathing rate)
Osmoregulation (maintains fluid balance)
Glucoregulation (maintains blood glucose)
What happens in thermoregulation with temperature increase?
Activates heat-loss centre in hypothalamus
→ blood vessels dilate sweat glands activates
→ body temp decreases and heat loss centre shuts off
What is the process of chemoregulation?
What is the process of osmoregulation?
What is the process of glucose regulation?
What is a positive feedback loop?
Magnifies original response instead of correcting it
What is an example of a positive feedback loop?
Childbirth- stretching of the cervix leads to more stretching, not less
What 2 systems does the circulatory system consist of?
Cardiovascular system
Lymphatic system
What is the cardiovascular system?
Heart and blood vessels transport blood through pulmonary circulation (lungs) and the systemic circulation (head and body)
What is the lymphatic system?
Lymph vessels transport excess fluid from body tissues towards heart (only one direction)
What are the 3 main components of the cardiovascular system?
Blood
Heart
Blood vessels
On average, how many litres of blood does a person have?
5
What are the 4 components of blood?
Plasma (55%)
Red blood cells (41%)
White blood cells (4%)
Platelets (0.01%)
What is in the plasma of blood?
Water
Plasma proteins (eg: albumin)
Ions, glucose, amino acids, hormones, gases, waste
What is another word for red blood cells?
Erythrocytes
What is another word for white blood cells?
Leucocytes
What are 5 different types of white blood cells?
Neutrophil (most common)
Lymphocyte
Basophil
Eosinophil
Monocyte
What is the structure of red blood cells- why?
Concave shape- extra surface area
No nucleus- adapted for extra SA
Where are all blood cells made?
Bone marrow
What is the most important function of blood?
Transport system
Brain and muscles that facilitate speech need continual supply of oxygen
What are 4 other functions of blood?
Clotting
Transports hormones, ions and nutrients
Transports heat around the body, stabilises
temperature
Transports white blood cells to sites of infection
What is the location of the heart?
Thoracic cavity
Mediastinal space
Posterior to sternum, between lungs, anterior to vertebral column
What are the 4 chambers of the heart?
Right atrium
Right ventricle
Left atrium
Right ventricle
What does the right atrium do?
Receives blood from body
What does the right ventricle do?
Pumps blood to lungs
What does the left atrium do?
Receives blood from the lungs
What does the left ventricle do?
Pumps blood to body
What does the septum in the heart do?
Separates right and left side?
Why does the left side of the heart have thicker cardiac muscle?
Higher pressure needed to pump blood around entire body
Same contractions have bigger effect due to the muscle
Where does the superior and inferior vena cava transport blood?
From head and body to right atrium
Where does the pulmonary artery transport blood?
From right ventricle to lungs
Where does the pulmonary vein transport blood?
From lungs to left atrium
Where does the aorta transport blood?
From left ventricle to body
What are the names of the 4 valves in the heart?
Tricuspid valve
Pulmonary valve
Mitral valve
Aortic valve
What do valves in the heart do?
Open and close in response to pressure of the blood as it is moved through the heart
Creates unidirectional blood flow, prevents backflow
What is the name of the natural pacemaker in the heart?
Sino-atrial node (SAN)
(bundle of electrically active cardiac cells)
How often does the sino-atrial node cause contractions?
Fires at 60-80 beats/min at rest
Where does the sino-atrial node cause contractions?
First contraction of the atria, followed by contraction of ventricles
What is the word for contraction / relaxation?
Contraction = systole
Relaxation = diastole
What is the process of contractions of the heart?
How does the nervous system control the cardiac cycle?
Sympathetic NS speeds heart rate
Parasympathetic NS slows heart rate
How long approximately does it take for blood to complete one circuit of pulmonary and systemic circulations?
1 minute
What are the 5 different types of blood vessels?
Arteries
Arterioles
Capillaries
Venules
Veins
What is the common 3-layer structure of blood vessels?
Tunica intima: smooth layer of squamous epithelial cells on base of collagen
Tunica media: smooth muscle
Tunica externa: protects outside
-> capillaries only have tunica intima
Which blood vessels carry HP blood away from the heart?
Arteries (elastic / muscular)
Arterioles
Which blood vessels carry LP blood towards the heart?
Veins (contain valves)
Venules
What does the thin wall of capillaries enable?
Diffusion of substances across capillary wall
Diameter 7-8µm
Label some main upper body arteries
What are the 4 parts to the aorta?
Ascending aorta
Aortic arch
Thoracic aorta
Abdominal aorta (from diaphragm down)
How is blood supplied to the brain?
R/L common carotid arteries branch into internal carotid arteries
How is blood supplied to the face/head/neck?
R/L common carotid arteries branch into external carotid arteries
How is blood supplied to the posterior of the brain?
Subclavian artery branch into vertebral arteries
What is blood pressure?
Pressure that blood exerts on the wall of the blood vessels
What is usual blood pressure?
90 - 120
60 - 80
What are the 2 types of blood pressure?
Systolic
Diastolic
What is systolic blood pressure?
Maximum pressure within the large arteries when the heart contracts
What is diastolic blood pressure?
Lowest pressure within the large arteries during heart muscle relaxation
How is blood pressure different in different blood vessels?
What 2 factors affect blood pressure in arteries?
Cardiac output
Peripheral vascular resistance
If cardiac output or peripheral vascular resistance increase, what happens to blood pressure?
Increases
What is cardiac output (CO)?
Volume of blood pumped by the heart in 1 minute (how effectively the cardiovascular system is working)
What does cardiac output depend on?
Heart rate
Stroke volume (amount of blood ejected from the LV in one contraction)
CO = HR x SV
What is peripheral vascular resistance?
Resistance to blood flow in the arterioles
Sympathetic stimulation → vasoconstriction → decreased diameter → increased PVR → higher blood pressure
Reduced sympathetic stimulation → vasodilation → increased diameter → decreased PVR → lower blood pressure
What do baroreceptors do?
Help maintain blood pressure via homeostasis
Where do baroreceptors sense stretch?
Carotid arteries
Aorta
If stretch in the carotid arteries and aorta are high…
BP is high
Baroreceptors sense → brain slows the heart + vasodilation of arterioles..
If stretch in the carotid arteries and aorta are low…
BP is low
Baroreceptors sense → brain speeds heart + vasoconstriction of arterioles
What are 5 pathophysiological effects of high blood pressure (hypertension)?
Atherosclerotic plaques and blood clots
Left ventricle hypertrophy
Aneurysms
Hypertensive retinopathy
Chronic kidney disease (CKD)
How does atherosclerotic plaques + blood clots occur from high blood pressure?
Damages endothelial cells lining arteries
Clots block coronary arteries → heart attack
Clots in brain → stroke
What are the 3 types of strokes?
Ischaemic stroke (85%)
Transient ischaemic attack (TIA)
Haemorrhagic stroke
What is an ischaemic stroke?
Blood clot forms on a ruptured atherosclerotic plaque, blocking blood flow to an area of the brain
What is transcient ischaemic attack?
Mini stroke
Temporary occlusion, the clot dissolves by itself
What is a haemorrhagic stroke?
Damage to blood vessels, leakage of blood into surrounding brain tissue
What is left ventricular hypertrophy?
Heart has to contract more to push blood through a high pressure system
Thicker walls = less blood
What are aneurysms?
Thinning and bulging of arteries
What is capillary exchange?
The exchange of substances between the blood and tissues in the capillaries
How does capillary exchange occur at the arteriole end?
Hydrostatic pressure: blood pressure forces fluid out containing nutrients + oxygen
How does capillary exchange occur at the venous end?
Oncotic pressure: fluid carrying CO2 is drawn back into capillary by osmosis (bcos higher concentration of protein solute (albumin))
What is the end result of capillary exchange?
Small net gain of tissue fluid/ extracellular fluid near cells
Extra fluid taken up by the lymphatic system -> returned to heart
How is excess tissue fluid removed by the lymphatic system?
Taken up into lymph vessel, taken back to veins near heart (superior vena cava), thus added back into blood circulation
What does lymph contain?
Tissue fluid (water, ions, urea)
Lymphocytes
Lipids from digestion
What do lymph nodes do?
Filters lymph on the way to the heart to detect any pathogens
What are the 2 primary lymphoid organs?
Thymus: site of T-lymphocyte maturation + release
Bone marrow: site of B-lymphocyte development + maturation
What are the 3 secondary lymphoid organs?
Tonsils: made mostly of lymphocytes, detects virus/ bacteria entering via mouth
Lymph nodes: made mostly of lymphocytes, detects virus/ bacteria in the lymph as it flows through
Spleen: made of red + white pulp, red filters out old red blood cells, white (made of lymphocytes) filters virus/bacteria from blood
What is the medical name for swollen lymph nodes?
Lymphadenopathy
What is the medical name for painful swollen lymph nodes?
Lymphadenitis
Why does lymphadenopathy occur?
Local infections
Upper respiratory infections
1% from cancer
What causes inflammation?
Damage to tissues
What is the vascular response to inflammation?
Vasodilation -> increases blood
flow, brings immune cells that release signals that activate nearby neurons, causing pain
Endothelial cell layer becomes leaky
and ‘sticky’ (so immune cells adhere)
What are the 4 cardinal signs of inflammation? Why do they occur?
Heat: extra blood arriving
Swelling: more fluid moving out into tissues by hydrostatic pressure, carrying immune cells
Redness: extra blood flow
Pain: stimulation of nearby neurons
What is a 5th cardinal sign of inflammation?
Immobility: due to swelling + pain
What are 5 main functions of the respiratory system?
Continuous supply of oxygen to cells
Removes waste gas (CO2)
Produces sound
Provides sense of smell
Protects airways from harmful substances + pathogens
How can the respiratory tract be divided?
Structure: upper respiratory tract + lower respiratory tract
Function: conducting zone + respiratory zone
What are the 3 components of the upper respiratory tract?
Nasal cavity
Pharynx
Larynx
How is the nasal cavity specialised to trap particles?
Nasal septum
Vestibule area (nostril) has stratified squamous epithelium (robust surface) + course hairs
How is the nasal cavity specialised to humidify/warm air?
Ciliated pseudostratified columnar epithelium cells (respiratory epithelium) and goblet cells (secretes mucous)
Rich blood supply under surface
How is the nasal cavity specialised to purify air?
Turbinates (conchae) inside the cavity increase surface area and swirl air, trapping particles of dust/pathogens
What are paranasal sinuses?
Extension of nasal cavity, linked by bony channels
Air filled cavities in the skull and bones around the nose- lined with columnar ciliated pseudostratified epithelium and goblet cells
What are the 4 paranasal sinuses?
Frontal sinus
Ethmoid sinus
Maxillary sinus
Sphenoid sinus
What are 3 purposes of paranasal sinuses?
Source of moisture (mucus) if nasal cavity is dry
Role in resonance (important for quality + tone of voice), thus why voice changes during a cold (extra mucus)
Makes skull lighter, frontal sinus acts as a crumple zone for cranium
What is the pharynx?
Muscular tube
Lined by ciliated pseudostratified columnar epithelium, with goblet cells, (also mucous glands)
What are the 3 parts of the pharynx superior to inferior?
Nasopharynx
Oropharynx*
Laryngopharynx*
- also in gastrointestinal system, as passageway shared for food and air
Describe the structure of the larynx
Connects pharynx with trachea
Lined by ciliated pseudostratified columnar epithelium
Reinforced by cartilage
What structures does the larynx contain?
Epiglottis: shuts of larynx during swallowing
Vocal folds (covered by stratified squamous epithelium): closes during swallowing, generates sound for speech
Describe the structure of the lungs
Right has 3 lobes: superior + middle + inferior
Left has 2 lobes: superior + inferior
Cardiac notch allows space for the heart in the mediastinal cavity
Hilum (medial lung surface): bronchi + pulmonary arteries enter, pulmonary veins exit
What are the 5 components of the lower respiratory tract?
Lungs
Trachea
Bronchi
Bronchioles
Alveoli
What is the pleura?
Double layered membrane surrounding each lung
What is the structure of the pleura membranes?
Visceral pleura: inner layer attached directly to lung surface
Parietal pleura: outer layer attached to chest wall + diaphragm + mediastinum, lines thoracic cavity
Diaphragmatic pleura: contacts the diaphragm
Pleural cavity: thin space between visceral/parietal pleura, filled with pleural fluid
What are the 5 functions of the pleura?
Lubrication: fluid minimises frictions between lung + chest wall, smooth movement during respiration
Surface tensions: maintains lung inflation by keeping 2 pleural layers adhered
Bond: fluid creates bond, so if thorax moves up + out pulls lungs with it to help expansion
Protection: barrier to separate lungs from other structures in thoracic cavity
Pressure regulation: negative pressure essential for lung expansion
What is the trachea?
Flexible tube 10cm long, 2cm wide
Lined by respiratory epithelium, interspersed by goblet cells
Stack of 16-20 C-shaped rings of hyaline cartilage, open part faces posterior to permit expansion of oesophagus during swallowing
Ends at carina bifurcation (divides to R/L bronchi)
What is the structure of bronchioles?
Smooth muscle + less cartilage, relies on elastic tissue for support
Epithelium becomes simple ciliated columnar, few mucous glands
Goblet cells replaced by clara/club cells, produces less viscous secretion
What is the structure of bronchi?
Cartilage + layer of smooth muscle
Lined by respiratory epithelium + goblet cells
Primary bronchi: R/L
Secondary bronchi: 3 in R, 2 in L
Tertiary bronchi: 10 in R, 8-10 in L
What are terminal bronchioles?
Smallest bronchioles
End of conducting zone
Ciliated simple cuboidal epithelium
Smooth muscle cells
Fewer goblet, more Clara
What are respiratory bronchioles?
First part of respiratory zone
Simple cuboidal epithelium
Contains small outpouchings (alveoli)
How are alveoli adapted for respiration?
Thin walls (simple squamous epithelium)- efficient gas exchange via diffusion
150mil alveoli /lung- huge surface area for diffusion
Extensive network of capillaries: covers each alveoli to allow diffusion across a wide area of the lungs
What are the different pneumocytes on alveoli?
Type I - thin simple squamous epithelium walls
Type II- lipid layer, fluid prevents alveoli collapsing in on itself
What is external respiration?
Exchange of O2 and CO2 between alveoli and pulmonary capillaries
What is internal respiration?
Exchange of O2 and CO2 between blood and tissues
What is the equation for cellular respiration?
Glucose + oxygen → carbon dioxide + water + ATP (+ heat)
Is ventilation automatic?
Yes but can override it by consciously changing breathing pattern
Pattern also changes during speech
What is ventilation?
Continuous movement of inspiration followed by expiration in a repeating cycle
What are the 3 most important structures for ventilation?
Diaphragm
Ribs
Intercostal muscles
What is the anatomy of the diaphragm?
Dome shaped muscle that separates the thoracic region from the abdominal region
Attaches anteriorly to ribcage, posteriorly to vertebral column
Openings to allow for descending aorta + ascending inferior vena cava + oesophagus
What does ventilation depend on changes in?
Volume and pressure in the thoracic cavity
What are the ribs?
12 pairs
Fairly mobile, through hinge joints with spinal vertebrae + cartilage joints with sternum
Allows movement up+out for inspiration, down+in for expiration
What is the sternum (breastbone)
Flat, midline of anterior thorax
Attached to ribs by costal cartilage
What is the vertebrae?
Spinal column
33, separated by fibrocartilage discs
What are the 5 divisions of the vertebrae?
Cervical (neck region): C1-C7
Thoracic (thorax): T1-T12
Lumbar: L1-L5
Sacral: S1-S5 fused
Coccygeal (coccyx region): 4 fused
How do the ribs attach to the thoracic vertebrae?
T1-T10 attach via costovertebral joints
T11-T12 floating ribs attach only to vertabral bodies
What is the role of the diaphragm?
Primary muscle of inspiration
Contraction = flattens, caused by phrenic nerve
How are the intercostal muscles connected to the ribs?
Each rib connected to rib below by 1 external intercostal muscle + 1 internal intercostal muscle
What does contraction of the external intercostal muscle do?
Elevates rib, spreads them apart
What does contraction of the internal intercostal muscle do?
Depresses ribs, pulls them closer
Used in forced expiration (not quiet breathing)
What is the breathing mechanism for inspiration?
External intercostal muscles contract
Ribs pulled up + out
Diaphragm pulled down
Lower pressure, higher volume
Air moves in
What is the breathing mechanism for expiration?
External intercostal muscles relax
Ribs pulled down + in
Diaphragm relaxes up
Higher pressure, lower volume
Air moves out
- pause, then inspiration starts again
What are the 3 accessory muscles for inspiration? (used for heavy exercise, shouting etc)
Sternocleidomastoid (elevates sternum)
Scalenes group (elevates upper ribs)
Pectorialis minor
What is the accessory muscle for expiration?
Abdominals
What are the 4 lung capacity measurements?
Inspiratory reserve volume
Tidal volume
Inspiratory reserve volume
Residual volume
What is the tidal volume?
Amount of air passing in/out of lungs during each cycle of quiet breathing
~500mL
What is the inspiratory reserve volume?
Largest volume of air inspired during forced inspiration, after the tidal volume
~3L
What is the expiratory reserve volume?
Largest volume of air expelled during forced expiration, after the tidal volume
~1.5L
What is the residual volume?
Volume of air in lungs after forced expiration, never completely empty
~1L
What is the inspiratory capacity?
Inspiratory reserve volume + tidal volume
What is the functional residual capacity?
Expiratory reserve volume + residual volume
What is one’s vital capacity?
Inspiratory reserve volume + tidal volume + expiratory reserve volume
Measure of lung health
Where is the respiratory centre located?
Brainstem
- medulla oblongata
- pons
What are the 2 regions of the medulla oblongata that controls respiration?
Ventral respiratory group (VRG)
- stimulates expiration by stimulating internal intercostal muscles + abdominal muscles when needed
- may also activate inspiration during heavy exercise
Dorsal respiratory group (DRG)
- stimulates inspiration by activating external intercostals + diaphragm
What are the 2 regions of the pons that controls respiration?
COntrols rate + depth of breathing…
Apneustic area
- stimulates inspiratory centre, prolonging contraction of inspiratory muscles
Pneumotaxic area
- inhibits inspiratory centre, limiting contraction of inspiratory muscles, prevents lungs overinflating
What are the 3 main factors affecting breathing rate?
Pulmonary stretch receptors
Peripheral chemoreceptors
Central chemoreceptors
How do the pulmonary stretch receptors affect breathing rate?
Lungs inflate, receptors detect pressure increase
Communicated to respiratory centre of brain
Inhibits apneustic area of pons
Inhibits inspiratory neurons in DRG
Allows expiration (passive recoil)
How do peripheral chemoreceptors affect breathing rate?
Aortic bodies in arch of aorta
Carotid bodies in carotid arteries
Detects changes in (low) O2 + (high) CO2 + (low) pH
Nerves end in medulla oblongata, in the tractus solitarius
- activates DRG to increase breathing rate to rid CO2
How do central chemoreceptors affect breathing rate?
In medulla, detects pH changes in cerebrospinal fluid (due to CO2 fluctuations)
- activates DRG
- activates VRG
Together, increased breathing rate to rid CO2
What are 5 other factors affecting breathing rate?
Emotional stress/anxiety (linked to symp NS)
Pain
Air resistance (eg: asthma)
Fever (increased O2 demand, increased BR)
Chronic Obstructive Pulmonary Disease (COPD)
What is the endocrine system made up of?
All the body’s different endocrine glands, tissues, and hormones
What are glands? What are the 2 types?
Structures made of epithelial cells that secrete a particular substance
Exocrine
Endocrine
Where do exocrine glands secrete fluid/ions/enzymes into?
A duct to another organ / outside the body (eg: tear duct)
Where do endocrine glands secrete hormones into?
The blood
What is an example of a gland that is both exocrine and endocrine?
Pancreas
Exocrine- pancreatic enzymes secreted into duct to small intestine
Endocrine- insulin into blood
What are the 3 types of hormones? Give examples for each
Protein: growth hormones, insulin, ADH
Steroid: oestrogen, progesterone, testosterone
Amine: thyroid hormone, adrenaline
What are protein hromones?
Water soluble (non-steroidal)
Several proteins joined in a polypeptide chain (smaller)
What are steroid hormones?
Lipid soluble
Synthesised from cholesterol
What are amine hormones?
Hormones derived from the modification of single amino acids
How do hormones work?
Carried in the blood to the target cells
- protein/amine bind to receptor on target cell membrane, series of reactions in cell, hormone moves to nucleus
- lipid dissolve, cross cell membrane and bind to receptor inside target cell
Change in genes expressed + activity of cell
What are some of the major glands in the endocrine system?
Which region of the brain is responsible for most endocrine control?
Hypothalamus main integrating centre that controls homeostasis of several hormones
ie: (regulating temp + fluid balance)
What is the anatomy of the pituitary gland?
Located in pituitary fossa in the skull
Connected to hypothalamus by a stalk known as infundibulum
2 lobes
- antieror pituitary (adenohypophysis)
- posterior pituitary (neurohypophysis)
Why is it important for the lobes of the pituitary gland to have rich blood supply?
Needs to release hormones into blood
What controls the release of hormones from the pituitary gland?
Neurons in the hypothalamus
What are the 6 hormones of the anterior pituitary?
Growth hormone (GH)
Thyroid stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Follicle-stimulating hormone (FSH)
Luteinising hormone (LH)
Prolactin
What is growth hormone (GH) essential for?
Growth in children
Metabolism regulation in adults
Acts on adipose + bone + muscle
What does thyroid-stimulating hormone (TSH) do?
Promotes synthesis of thyroid hormones crucial for metabolism + energy regulation
What does follicle-stimulating hormone (FSH) do?
Gamete production in males and females
Females- stimulates oestrogen secretion, maturation of follicle
Males- sperm maturation
What does luteinising hormone (LH) do?
Triggers ovulation + secretion of progesterone in females
Triggers testes for testosterone production in males
What does prolactin do?
Stimulates milk production in lactating females + affects reproductive functions
What are the 2 hormones of the posterior pituitary?
Oxytocin
Antidiuretic hormone (ADH) / vasopressin
What does oxytocin do?
Crucial role in childbirth + lactation
Stimulates urine contractions + milk ejections
Also: love/bonding hormone kept through evolution
What does ADH / vasopressin do?
Regulates water retention in the kidneys (constricts blood vessels, thus controls BP + fluid balance)
What is the anatomy of the thyroid gland?
Neck regin
Highly vascularised (good blood supply)
Follicular cells secrete thyroxine
Parafollicular/C-cells secrete calcitonin (if blood calcium high)
What are the 2 forms of thyroid hormones?
T4 (thyroxine) -inactive
T3 (triiodothyronine) -active
- all T4 converted into T3
How does T3 act on all cells of the body?
Increasing metabolic rate + heat production
What is thyroid hormone essential for?
Normal growth and development
Healthy brain function
How does thyroid hormone (TH) levels fluctuate daily?
Highest after waking up (starts metabolism + E production for the day)
Decreases during the day, falls at night
What is the negative feedback for when thyroid hormone (TH) falls at night?
Hypothalamus detects ↓ TH
Hypothalamus releases thyrotropin-releasing hormone (TRH)
TRH signals pituitary to release TSH
TSH acts on thyroid to ↑ TH
What can surgery on the thyroid gland affect?
Vocal cords, as close to larynx
What are the 2 thyroid disorders that can affect speech?
Hyperthyroidism (high TH)
Hypothyroidism (low TH)
How does hyperthyroidism affect speech/swallowing?
Higher metabolic rate
- high pitched, tremulous, uneven intonation, vocal fatigue
- swelling of thyroid can compress trachea -> dysphagia
How does hypothyroidism affect speech/swallowing?
Lower metabolic rate
- retarded laryngeal development + muscle atrophy -> weak voice
- oedema (fluid retention) in vocal tract may prevent complete closure of larynx during phonation + poor articulation from tongue/lip swelling
- swelling of thyroid can compress trachea -> dysphagia
Where are the parathyroid glands located?
2 glands (4 total) on posterior thyroid lobes
What hormone do the parathyroid glands secrete?
Parathyroid hormone (PTH) when blood calcium (Ca2+) low
PTH stimulates osteoclasts (bone cells) to release calcium from bones to blood
What is the anatomy of the adrenal glands?
Located on top of each kidney
Adrenal cortex + adrenal medulla + connective protective capsule
What is the hypothalamic-pituitary-adrenal axis?
ACTH from anterior pituitary stimulates adrenal cortex to secrete glucocorticoids (mainly cortisol)
- increases glucose + protein + lipid availability in stressful situations (more nutrients for energy)
When cortisol rises, hypothalamus inhibits ACTH from pituitary
What hormones does the adrenal medulla release?
Adrenaline (epinephrine)
Noradrenaline (norepinephrine)
Which part of the brain controls the adrenal medulla?
Neural control form hypothalamus- doesn’t involve other hormones so released in seconds
What does adrenaline do?
Releases a short burst of ATP in muscle cells
- increases cardiac activity
- increases skeletal muscle activity
What does noradrenaline do?
Increase blood pressure
What is the short term stress response?
Heartbeat and BP increase
Blood glucose level rises
Muscles become energised
What are the specialised cells in the pancreas?
Alpha cells and beta cells in the Islets of Langerhans
How do beta cells help glucose regulation?
Secrete insulin when blood glucose high
- uptake of glucose in muscle + liver + fat cells
- liver + muscles store glucose as glycogen (glycogenesis)
Lowers blood glucose
How do alpha cells help glucose regulation?
Secrete glucagon when blood glucose low
- stimulates liver to convert glycogen back to glucose (glycogenolysis)
- promotes glucose production from non-carbohydrate sources (gluconeogenesis)
Increases blood glucose
What is the negative feedback control of LH and FSH called?
Hypothalamic-pituitary-gonadal axis
How does testosterone affect the male voice?
Increased size of the thyroid cartilage of the larynx
Adam’s apple prominent
Vocal folds elongated -> lower pitch + deeper voice
What are the 3 main functions of the nervous system?
Processing info and communication- receives sensory input from in/external environment, integrating system so formulates + executes appropriate responses using effectors
Significant role in homeostasis
Involved in higher processes
What is the organisation/divisions of the nervous system?
What does the brain do?
Receives and processes info
Initiates responses, stores memories, generates thoughts + emotions
What does the spinal cord do?
Conducts nerve impulses to/from brain
Transmits nerve impulses to/from body
Controls reflex actions
What does the peripheral nervous system consist of?
All nerves outside the brain, connecting CNS to limbs + organs
What does the somatic nervous system consist of?
Spinal nerves: 31 pairs
- emerge from spinal cord- transmits sensory + motor signals b/w CNS and rest of body
Cranial nerves- 12 pairs
- emerge from brain + brainstem- transmits sensory + motor signals b/w CNS and head&neck, and automatic functions
What does the somatic nervous system do?
Sensory input: transmits sensory info from skin/muscles/joints to CNS -> we perceive touch/pain/temperature/body position
Motor output: controls voluntary movements by connecting CNS to skeletal muscles
What does the sympathetic branch of the ANS do?
Reaches virtually all body parts
Innervates both sides of the spinal cord
Fight or flight responses in organs + tissues
What does the parasympathetic branch of the ANS do?
More localised to certain organs + glands
Innervates both sides of the spinal cord
Rest and digest responses in organs + tissues
How does the sympNS and parasympNS work together?
Like a dial, one more prominent than the other
What are the 3 main brain regions?
Cerebrum
Brainstem
Cerebellum
also…
forebrain: cerebrum
midbrain: midbrain (superior brainstem)
hindbrain: pons, medulla, cerebellum
What are the 3 parts of the brainstem?
Midbrain
Pons
Medulla oblongata
What does the cerebellum do?
Coordinates movement of all muscle groups
What is the cerebral cortex?
Outermost layer of the cerebrum
Dense layer of interconnected neurons (grey matter) which process & respond to info
What are the 5 lobes of the cerebrum?
Frontal lobe
parietal lobe
Temporal lobe
Occipital lobe
Insula lobe
- all pairs
What are the 5 functions of the frontal lobe?
Executive functions
Emotional regulation (impulse control)
Motor function
Speech
Moral judgement
What is the function of the parietal lobe?
Integrates sensory info (touch, temp, pressure, pain)
What is the function of the occipital lobe?
Major visual processing centre
What are the 3 functions of the temporal lobe?
Hearing
Recognising language
Forming memories
Where does the insula lobe lie?
Under the fissure between the frontal and temporal lobes
What are the 3 functions of the insula lobe?
Regulating desires/emotion/mood/behaviour
Sensory processing
Planning + execution of speech movements
How is the surface of the brain described? What does it have on it?
Convoluted (not smooth)
Gyrus- raised area
Sulcus- groove
Fissure- deep groove
What are 2 notable gyri?
Pre-central gyrus (motor cortex)
Post-central gyrus (sensory cortex)
What is a notable fissure?
Longitudinal fissure: divides brain into R/L hemispheres
What are 3 notable sulci?
Central sulcus: between frontal and parietal lobes
Lateral sulcus (Sylvian fissue): between frontal and parietal, and temporal lobes
Parieto-occipital sulcus: between parietal and occipital lobes)
What are 6 major regions on the cerebral cortex?
Primary motor cortex (frontal)
Primary somatosensory cortex (parietal)
Visual cortex (occipital)
Auditory cortex (temporal)
Olfactory cortex (temporal)
Gustatory cortex (insula)
What does the primary motor cortex do?
Executes motor functions for skeletal muscle
What does the primary somatosensory cortex do?
Receives sensory info from the somatic NS (pain temperature, pressure, vibration, joint location)
What are the 2 areas of the brain responsible for speech and language?
Broca’s area: left frontal lobe
Wernicke’s area: left temporal lobe
note: dotted lines = associated areas, not specifically there
note: close together as they act together
What is Broca’s area for?
Linguistic encoding: thoughts / ideas/ sensory experiences converted into language for communication
Production of speech / written language
What is Wernicke’s area for?
Spoken / written language comprehension
Monitoring of speech production
What are Brodmann areas?
52 regions of cerebral cortex mapped + defined based on unique cellular structures and organisation
What is the corpus callosum?
Thick bundle of neurons that connects R+L hemispheres
Enables transfer of info (sensory/motor/cognitive) between R+L hemispheres
What does the arcuate fasciculus do?
Connects Wernicke’s and Broca’s
What can damage to the areas of the brain responsible for language (Broca / Wernicke) result in?
Broca’s aphasia
Wernicke’s aphasia
What can damage to the arcuate fasciculus lead to?
Conduction aphasia: affects communication between areas
Where is the medulla oblongata located?
Continuous with spinal cord through foremen magnum (hole in base of skull)
Superiorly, its continuous with pons
What are the 5 distinguishing anatomical features of the medulla?
Cardiovascular + respiratory centres
Pyramidal tract (motor) decussation
Dorsal column (sensory) decussation
Medullary olives
Reticular formation
How is brainstem anatomy viewed?
Transverse planes
Each part then further divided to look at features of dif levels: eg medulla…
Where is rostral?
How does the respiratory centre in the medulla work?
DRG and VRG controls muscles of respiratory system to stimulate ventilation
How does the cardiovascular centre in the medulla work?
Receives info about BP: increases / decreases heart rate and peripheral vascular resistance
What are the medullary pyramids?
2 large bundles of nerves travelling from motor cortex to spinal cord
First pass through midbrain + pons
Travel down + medially to anterior of medulla as 2 ridges
What is the pyramidal decussation?
Lower part of medulla oblongata
Pyramids (motor fibre bundles) cross (decussate) to opposite side posteriorly and laterally
Motor neurons control opposite side of body (contralateral)
What are the dorsal columns?
Bring somatosensory info from spinal cord to medulla
At medulla level: 4 dorsal column nuclei
What happens at the dorsal column nuclei?
Synapse where neurons travel anteriorly and decussate at medial lemniscus, up to thalamus via medial lemniscus tract
Where are the medullary olives located?
Upper part of medulla
2 oval-shaped nucleus (group of neurons) on each side
What do the medullary olives play a crucial role in?
Coordination + learning by transmitting signals to cerebellum
Particularly for fine tuning motor skills
What is the reticular formation?
Network of nerve fibres + nuclei spread throughout brainstem (and sensory + motor system)
What is a function of the reticular formation?
Coordinate reflexes + posture by interacting with motor pathways, assisting in balance + movement
What does the pons do?
Acts as a bridge between cerebral cortex and cerebellum
What are the 2 important pathways in the pons?
Motor tracts descending from motor cortex
Sensory tracts travelling up from spinal cord, some connect with reticular formation
What are the 4 anatomical features of the midbrain?
Cerebral peduncles
Tectum
- these areas separated by cerebral aqueduct
Red nuclei
Substantia nigra
What is the cerebral aqueduct?
Central spinal fluid channel
What are the cerebral peduncles?
Large bundle of motor axons traveling down from cortex to spinal cord (will form pyramids)
What are the 2 parts of the tectum?
Superior colliculi
Inferior colliculi
What does the superior colliculi do (tectum)?
Receives input from optic nerves
Coordinates eye + head movements to follow objects in visual fields
What does the inferior colliculi do (tectum)?
Coordinates auditory reflexes: turns head towards a sound source
What does the red nuclei do?
Grey matter connecting cerebellum + motor cortex with descending motor pathways
Allows info on the state of contraction + stretch of muscles to be fed to motor pathway
What are the substantia nigra?
Grey matter part of the basal nuclei/ganglia, involved in movement control
What is the cerebellum involved in?
Control of motor activity
Learning motor skills
Balance
- by controlling rate + range + force of muscular activity
What are the cerebellar peduncles?
Bundle of nerves connecting to brainstem
What do each of the 3 cerebellar peduncles connect the cerebellum to?
Superior cerebellar peduncles: cerebral hemispheres
Middle cerebellar peduncles: pons
Inferior cerebellar peduncles: medulla oblongata
What are the 3 lobes in the cerebellum?
Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
What is the vestibulocerebellum?
Connected to brainstem via inferior cerebellar peduncles: involved in balance (links to info from ears)
What is the spinocerebellum?
Connected to brainstem via superior cerebellar peduncles: influences muscle tone + posture
What is the cerebrocerebellum?
Connected to brainstem by superior + middle cerebellar peduncles: helps plan + coordinate precise, smooth movements
What is the basal ganglia?
System of nuclei located deep in each cerebral hemisphere + midbrain
Whata are the 3 parts of the basal ganglia?
Caudate nucleus
Lentiform nucleus
- globus pallidus
- putamen
Substantia nigra
What does the basal ganglia do? Mention 2 disorders that can be affected if the basal ganglia doesn’t work properly
Coordinating smooth + steady movements: slows & coordinates
if too slow… Parkinson’s
if too jerky… Huntington’s
What is the spinal cord protected by?
Vertebrae bones of the spine and vertebral discs (fibrous cartilage)
What are the 5 spinal cord regions?
Cervical: C1-C8
Thoracic: T1-T12
Lumbar: L1-L5
Sacral: S1-S5
(Coccygeal- 1 pair)
How do you determine how severe a spinal injury is?
Lower down = less parts of the body affected = less severe
note: can hit spine just one side
How can a spinal injury in the thoracic region affect speech?
Affects intercostal muscles: hard to build pressure needed for speech
What is quadriplegia?
Cervical injury: paralysis from neck down
What is paraplegia?
Thoracic injury: paralysis from trunk down
What are the spinal nerves?
31 pairs connected to spinal cord
Facilitates communication between brain and body
What are the 4 main spinal nerve plexuses?
Cervical
Brachial
Lumbar
Sacral
- each give rise to other peripheral nerves
What do nerve plexuses do?
Form intricate networks that innervate specific regions of the body, allows communication between these regions & brain
What are some of the main features in a spinal cord transverse plane?
White and grey matter
Ventral and dorsal horns
Paired spinal nerves
* Sensory enters dorsally
* Motor nerves exit ventrally
What is the white matter of the spinal cord divided into?
Motor/sensory tracts
What are the 4 different neuroglia in the CNS?
Oligodendrocytes
Astrocyte
Ependymal cells
Microglial cells
What do oligodendrocytes do?
Produce myelin sheath in the CNS
What do astrocytes do?
Support + repair neurons, involved in homeostasis in CNS
What do ependymal cells do?
Production + flow of cerebrospinal fluid (CSF)
Brain metabolism
Waste clearance
What do microglial cells play a role in?
Immune function
What are the 2 different neuroglia in the PNS
Satellite cells
Schwann cells
What do satellite cells do?
Support + repair neurons, involved in homeostasis in PNS
What do schwann cells do?
Form myelin sheath in the PNS
What do neuron cells do?
Transmit impulses within CNS and PNS (very well adapted to do this!)
What are the 8 parts of the neuron cell?
Cell body
Cell membrane
Dendrite
Axon
Axon terminal
Synapse
Myelin Sheath
Nodes of Ranvier
What is the cell body in the neuron cell?
Cytoplasm, nucleus, orgnelles
What is the cell membrane in the neuron cell?
Phospholipid bilayer around the whole cell
What does the dendrite in the neuron cell do?
Receives incoming signals from other neuron’s axon terminal
What does an axon in a neuron do?
Carries outgoing signal to axon terminal
What is the axon terminal?
Area of the cell membrane at the very end of the axon
What is the synapse?
End of axon terminal which communicates with dendrites on other neurons
What is the myelin sheath?
Not part of neuron itself, wraps around axon of many neurons
Protective fatty insulating layer -> impulses travel faster + more efficiently along axon
What are the Nodes of Ranvier?
Nodes between myelinated regions/segments, no coverage
Helps move impulse up neuron
What is myelin made from?
Nearby neuroglial cells
Their phospholipid bilayer membranes are lipids, creates lipid sheath known as myelin
What happens to those with multiple sclerosis (MS)?
Immune system (or microglial cells) attacks myelin sheath
How can multiple sclerosis (MS) affect speech?
Nerves in face + neck are myelinated
What matter is unmyelinated neurons?
Grey matter
What are the 3 different types of neurons?
Sensory neurons (afferent)
Relay neurons (interneurons)
Motor neurons (efferent)
What do sensory neurons do?
Carry info from periphery to CNS
What do relay neurons do?
Form links between other neurons in CNS
What do motor neurons do?
Carry info from CNS to muscles and glands to cause an effect
What are some examples of sensory neurons?
What’s some examples of a motor neuron?
What is a nerve made of?
Bundles of individual neuron cells, with blood vessels and connective tissue
What are the 3 layers of a nerve?
Endoneurium: covers individual neurons
Perineurium: covers each buncle
Epineurium: outer layer of nerve
How do impulses travel along neurons?
Action potentials (electrical impulses)
In myelinated neurons, how fast do impulses travel?
Up to 250 miles/h
How are neurons at rest polarised?
Inside the cell has fewer positive charges (charges are mostly ions)
Inside the cell is -70mV in respect to the outside
How do action potentials travel?
Saltatory conduction- from node to node (unmyelinated regions)
How are neurons polarised at rest with a -70mV membrane potential?
Na+K+ pumps
- pump 3Na+ out of cell
- pumps 2K+ into cell
- Na+ channels closed so most sodium cannot enter at rest
- some K+ leaks out
Sone proteins inside cell have negative charge
What happens when a neuron receives a stimulus (smt from environment)?
Sodium ion channels in membrane get disturbed by stimulus and open up
Sodium ions flow into neuron, creating a more positive voltage inside the cell
How does a stimulus initially cause ions to enter a resting neuron?
Physical pressure
Chemical (ligand) binding
What is the threshold potential for an impulse to be initiated down a neuron?
-55mV
Initial stimulus must cause enough sodium ions to flow into the cells to raise the membrane potential
How was the threshold potential of -55mV reached?
Via evolution, ie: bugs on skin not a bug enough threat
One the full depolarisation occurs, what voltage is the inside of the cell?
+40V
note: some sources say +30mV?
What are failed initiations?
Stimulus too small to reach the threshold of -55mV
Only caused small depolarisation- not enough to trigger full depolarisation: all or none principal
What is depolarisation?
Voltage-gated Na+ channels open
Positive charges flowing into the cell cause membrane potential to increase
What is repolarisation?
K+ ions move out because neuron has to return to polarised (resting) state rapidly so it can receive another stimulation
Can a new action potential be fired during the hyperpolarisation period?
No, freezes so inactive for a short time
Because it is too negative, can’t raise to -55mV
Ensures signal doesn’t go backwards
What is hyperpolarisation (refractory period)?
K+ ions continue t move out
Inside of cell becomes more negative than resting state (undershoots)
Na+K+ATPase pump quickly returns K+ and Na+ to resting position at around 3ms
What are the 2 factors affecting the speed of impulses?
Axon diameter
Myelin
How does an action potential propagate along an axon? (also known as nerve impulse activation)
Sodium channels along axon are voltage gated (sense △voltage on inside of cell)
As voltage changes and gets more positive inside the cell, nearby voltage gated Na+ channels open, allows another rush of Na+ in cell
How does axon diameter effect the speed of impulses?
Greater diameter = faster speed
How does myelin affect the speed of impulses?
Myelin acts as an insulator
Depolarisation spreads more rapidly up neuron when myelinated
The activation of voltage-gated ion channels jumps from one node of ranvier to next
note: distance between nodes has evolved via evolution
What is a synapse?
Location where axon terminal of one neuron communicates with…
- dendrite of another neuron
- muscle tissue
What does the axon terminal form?
A bouton (swelling)
What is a synaptic cleft?
Tiny gap between the bouton of the axon terminal and the dendrite of the neighbouring neuron
How wide is the synaptic cleft? Why is it there?
20-50nm
Prevents activation of nearby neurons, instead a neurotransmitter is released
Why is there mitochondria in the axon terminal?
To provide energy for neurotransmission
What channels are in the membrane of the axon terminal?
Voltage-gated calcium (Ca2+) channels
Open in response to change in voltage (when wave of depolarisation travels down axon and reaches axon terminal)
What happens when voltage-gated calcium channels in the axon terminal open?
Ca2+ enters axon, causing release of vesicles containing a chemical neurotransmitter into synaptic cleft
note: one neuron can release several types of neurotransmitters
What are the neurotransmitter receptors called?
Ligand-gated ion channels
Open in response to neurotransmitter molecule binding into receptor shape
What happens when ligand-gated ion channels on the post-synaptic membrane open?
Ions rush into cell
What are the 2 post-synaptic channels?
Sodium channels
Chloride channels
What happens if sodium channels are opened by the neurotransmitter binding?
Sodium enters the cell to produce a positive voltage: depolarisation more likely (stimulation/ excitation)
Produces an excitatory post-synaptic potential (EPSP)
What happens if chloride channels are opened by the neurotransmitter binding?
Chloride enters the cell to produce a negative voltage: depolarisation less likely (inhibition)
Produces an inhibitory post-synaptic potential (IPSP)
What voltage does an inhibitory post-synaptic potential lower the membrane potential to?
~ -90mV
This stops depolarisation as nearly impossible to raise to -55mV
What is an example of an excitatory neurotransmitter in the sympathetic nervous system?
Noradrenaline
Used between postsynaptic neurons and target tissues
What is an example of an excitatory neurotransmitter in the parasympathetic nervous system?
Acetylcholine (ACh)
Used between postsynaptic neurons and target organs
What is an example of an excitatory neurotransmitter in the CNS?
Glutamate
What are 2 examples of inhibitory neurotransmitters in the CNS?
Gamma amino butyric acid (GABA)
Glycine
Why do neurotransmitters need to be removed from the synaptic cleft?
Prevent repeated transmission and overstimulation of post-synaptic terminal
How are neurotransmitters inactivated / removed from the synaptic cleft? (2 ways)
Enzymes destroy neurotransmitter
Reuptake of neurotransmitter into presynaptic neuron
Give an example of neurotransmitters being inactivated by enzymes that destroy the neurotransmitter
Acetylcholinesterase is an enzyme that breaks down excess Acetylcholine in the synapse
Give an example of neurotransmitters being inactivated by reuptake of the neurotransmitter into the presynaptic neuron
Excess glutamate is taken back up by glutamate re-uptake channel
Why do neurons form complex networks in the brain?
~ 100 billion neurons in the brain
May receive both excitatory + inhibitory signals
What is convergence of neurons?
Many presynaptic nerves synapse on the same post-synaptic nerve
Info is received from many neurons
What is divergence of neurons?
Presynaptic axon contacts several post-synaptic neurons
Info is spread
What is a neuromuscular junction?
Motor neurons form a synapse with muscle cells to cause them to contract
Each branch of the axon terminal will synapse with a motor end plate on the muscle tissue
What neurotransmitter does voluntary muscle contraction require?
Motor neuron must release acetylcholine from synaptic vesicles into the synaptic cleft to initiate voluntary muscle contraction
What are motor neurons needed for?
Voluntary muscle contraction (somatic NS)
Involuntary muscle contraction + stimulation of glands (autonomic NS)
What are the other inputs into motor neurons as they pass through the CNS? (think convergence)
Eyes
Vestibular apparatus (ears)
Cerebellum (posture/balance)
Basal ganglion loop system
What is the hierarchy of motor pathways?
Primary motor cortex
Upper motor neurons
Lower motor neurons
What are upper motor neurons?
Axons from the primary motor cortex descending directly to the brainstem or spinal cord
What are the lower motor neurons that exit at the brainstem?
Cranial nerves: innervates muscles of head + neck
What are lower motor neurons?
Receive an impulse from an upper MN at a synapse, and then exit the CNS to cause contraction of a muscle/gland in periphery
What are the lower motor neurons that exit from the spinal cord?
Spinal nerves: innervates muscles of lower body
note: exits from ventral horn of grey matter
What are the 3 areas of the frontal lobe involved in motor movement?
Primary motor cortex (M1)
Premotor cortex (PM) - lateral anterior
Supplemental motor area (SMA) - medial anterior
What does the premotor cortex do?
Receives sensory input from parietal lobe + basal ganglia
Helps plan + prepare movement
What does the supplemental motor area do?
Coordinates complex fine movements and posture
How is the primary motor cortex arranged?
Somatopically: correct sequence but upside down
Area of cortex devoted to area reflects degree of skills movement the area is capable of (motor homunculus)
What are the 2 types of motor tracts in the white matter of the spinal cord?
Lateral motor tracts
Medial motor tracts
What is the other way of dividing the motor tracts?
Pyramidal (from cerebral cortex: corticospinal tracts)
Extrapyramydial (from brain stem)
What are the 2 main lateral tracts that both descend on each side of the spinal cord?
Lateral corticospinal tract
Rubrospinal tract
Where does the lateral corticospinal tract start, and describe its path?
Main corticospinal tract starts in the motor cortex
85% of fibres decussate in the medulla to form the lateral corticospinal tract
- rest of the anterior corticospinal tract
What does the rubrospinal tract originate, and describe its path?
Red nuclei in the midbrain
As fibres emerge, they decussate and descend into the spinal cord, so innervate contralateral muscles
What is the main function of the lateral corticospinal tract?
Skilled + fine motor control in the upper and lower distal area of limbs (fingers and toes)
What is the main function of the rubrospinal tract?
Controls voluntary flexor muscles of the limbs (muscles that bend limbs for movement)
What are the 3 overall functions of medial motor tracts?
Balance and posture
Proximal limb muscles
Guiding limbs into planned movements
- lots of involuntary movement, but some aspects voluntary
What are the 4 medial motor tracts?
Ventral (anterior)
corticospinal tract
Medial reticulospinal tracts
Tectospinal tract
Vestibulospinal tract
What happens to the ventral/anterior corticospinal tract at the decussation of pyramids?
Carries on ipsilaterally through the medullary pyramids and only decussates at the spinal cord level as synapses onto lower motor neuron (ultimately has contralateral effect)
What are the functions of the ventral/anterior corticospinal tract?
Maintain posture + balance
Purposeful voluntary movements, esp in trunk/neck/shoulder regions
Where do the 2 reticulospinal tracts originate from, and what do they stimulate?
Medial/pontine reticulospinal tract
- reticular formation of pons
- stimulates extensor muscles
Lateral/medullary reticulospinal tract
- reticular formation of medulla
- stimulates flexor muscles
Where do the reticulospinal tracts receive sensory inputs from?
Spinoreticular tracts (sensory)
Red nuclei
Motor cortex
What is the function of the reticulospinal tracts?
Work together to coordinate movement of upper + lower limbs
Where does the tectospinal tract originate, and describe its path?
Originates at superior colliculus in midbrain
Decussates in midbrain, descends into spinal cord
Terminates at cervical level of spinal cord
What do the tectospinal tracts do?
Controls reflex postural movements in the head + neck mainly in response to sounds / visual stimuli
Where does the vestibulospinal tract originate, and describe its path?
Vestibular nuclei (pons + medulla)
Tracts convey balance info to spinal cord, remains ipsilateral
Where do vestibular nuclei (vestibulospinal tract) receive info about?
Balance from the semi-circular canals
Back from vestibulocerebellum to modulate / refine motor output
How does the vestibulospinal tract control balance + posture?
Innervating anti-gravity muscles in trunk + spine to maintain upright posture
Responding to changes in head position + movement for reflexive adjustments to prevent falls
What is the motor pathway for cranial nerves called?
Corticobulbar tract
Where does the corticobulbar tract originate, and describe its path?
Originates in primary motor cortex, follows same pathway down towards medullary pyramids
Branches come off at dif levels to terminate on motor nuclei in: midbrain, pons, medulla
Here, they synapse with lower MN, which are the dif cranial motor nerves
What do the cranial nerves control? (voluntary)
Facial expression
Mastication (chewing)
Swallowing
Vocalisation + speech
What type of control is most of the cranial nerves?
Bilaterial: coordinated movements on both sides of the face and head
note: can accomodate in stroke
but- lower facial + hypoglossal only give contralateral innervation
How are the corticospinal and corticobulbar tracts similar?
Both begin in cerebral cortex and receive range of inputs from M1 + PM + SMA + nerve fibres from somatosensory area
Share a common pathway: pass through internal capsule and descend to anterior midbrain
What is the internal capsule?
White matter structure
Densely packed bundles of nerve fibres, primarily ascending + descending axons (ie: cortispinal + bulbar)
Major pathway for communication
Where does the internal capsule receive its blood supply? Why is this important?
Series of small perforating arteries entering at base of brain
Susceptible to a compression from strokes (capsular stroke) -> can cause lesion in descending (motor) tracts
What are the 5 components of the somatosensory (touch) sense?
Thermoception (temperature)
Nociception (pain)
Equlibrioception (balance)
Mechanoreception (vibration/ discriminatory touch/ pressure)
Proproiception (position + movement)
What are the 6 senses in the multimodel sensory system?
5 special senses…
- gustation (taste)
- ocular (visual)
- olfaction (smell)
- vestibular (balance)
- auditory (hearing)
Somatosensory
What are the 4 components of proprioception?
Joint position
Kinaesthesia (movement)
Sense of force
Sense of change in velocity
Where is sensory info from each special sense processed?
Thalamus (except olfaction)
Then sent to relevant area of cortex
How is somatosensation sensed?
Receptors on body surface/ joints/ muscles
Interoception = sensation inside the body
Exteroception = sensation outside the body
What are the 2 different types of sensations from inside the body?
Proprioception (somatosensation)
Viscerosensation (from autonomic NS)
What does the sensory homunculus map represent?
Where sensory info from different regions are processed
Disproportionate amount of cortex area dedicated to dif body parts based on sensory input
What is sensory mapping?
Dermatomes
Each segment of the spinal cord receives sensory info from one dermatome (particular area of body)
e.g. somatosensory
information from the
lower leg will enter the
spinal cord at L5
Describe cell bodies on sensory neurons
Outside the spinal cord
Form a swelling: dorsal root ganglion
Sensory neurons enter spinal cord at dorsal root
What are the 2 main sensory tracts?
Dorsal column medial lemniscus (DCML) tract
Antero-lateral tracts
- spinothalamic tracts
- spinoreticular tract
What does the dorsal column medial lemniscus (DCML) tract sense? (5)
Discriminative (fine) touch
Texture
Vibration
Pressure
Proprioceptive info
How is the dorsal column medial lemniscus (DCML) tract arranged?
Fasciculus gracilis (medial): carriers sensory info from lower body T6↓
Fasciculus cuneatis (lateral): carriers sensory info from upper body T6↑
What matter is the dorsal column medial lemniscus (DCML) tract made of?
White matter (myelinated: feels almost instantaneous)
How many neurons are in the dorsal column medial lemniscus (DCML) tract?
3, contralateral
What is the 3 neuron DCML tract?
1st order neuron: from body into dorsal tract and ipsilaterally up to medulla to dorsal column nuclei
2nd order neuron: synapse in medulla with medial lemniscus tract, decussates, then up to thalamus
3rd order neuron: synapse, travels up to correct region of somatosensory cortex
What are the 4 anterolateral tracts? What matter are they?
Lateral spinothalamic
Anterior spinothalamic
Lateral spinoreticular
Anterior spinoreticular
White matter tracts
What does the lateral spinothalamic tract control?
Pain
Temperature/thermal sensations
What does the anterior spinothalamic tract control?
Crude touch
Deep pressure sensations
What is the 3 neuron spinothalamic tract?
1st order neuron: from body into dorsal horn, synapses
2nd order neuron: crosses spinal cord (decussates), then ascends straight up to thalamus, synapses
3rd order neuron: travels up from thalamus to correct region of somatosensory cortex
What do both spinoreticular tracts do?
Transmit pain + temperature sensations from spinal cord to reticular formation in brainstem
What does the lateral spinoreticular tract control?
Autonomic + emotional responses to pain
What does the anterior spinoreticular tract control?
Pain modulation + behavioural responses (ie: protective mechanisms to help pain/learn to not do something)
What is the 4 neuron spinoreticular tract?
1st order neuron: from body into dorsal horn, synapses
2nd order neuron: crosses spinal cord (decussates), ascends up to reticular formation, synapses
3rd order neuron: travels up from reticular formation to thalamus
4th order neuron: travels up from thalamus to widespread areas of cortex + hypothalamus
What are the 12 cranial nerves?
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal
What is the function of the olfactory nerves?
Special sense of smell
What types of nerve fibres are in the olfactory nerves?
Sensory only
What is the origin of the olfactory nerves?
Olfactory receptor cells send signals → olfactory bulb (ipsilateral)
What does damage to an olfactory nerve result in?
Unilateral anosmia (loss of smell in 1 nostril)
How can damage occur to the olfactory nerves?
Head injuries
Infections
Nasal polyps
Tumours
Chemical exposure
What are the clinical tests for the olfactory nerves?
Odour identification test: strong smelling substances held under nose, close other nostril
Scratch and sniff test: scratch panel to release sent, identify whilst closing other nostril
What is the function of the optic nerves?
Transmits electrical impulses form eyes to brain
What type of nerve fibres are in the optic nerves?
Sensory only
What is the origin of the optic nerves?
Retina of eye → optic canals of sphenoid bone → diencephalon via optic chiasm
What are the different visual fields- where do they hit, and do they cross at the optic chiasm?
Temporal VF hits nasal retina → crosses optic chiasm
Nasal VF hits temporal retina → doesn’t cross optic chiasm
What does damage to the optic nerve before it crosses result in?
Blindness in ipsilateral eye
What does damage to the optic chiasma result in?
Bilateral hemianopia (loss of temporal visual fields)
What does damage to the visual cortex result in?
Complex visual losses
How can damage occur to the optic nerves?
Pituitary tumours
Stroke
TBI
Dementia
Vascular abnormalities
Inflammation
What are the clinical tests for the optic nerves?
Snellen charts + testing visual fields (4 quadrants of each eye)
What is the function of the oculomotor nerves, trochlear nerves, and abducens nerves?
Controls several muscles of the eye
What types of nerve fibres are in the oculomotor nerves, trochlear nerves, and abducens nerves?
Motor to extraocular muscles of eye
Oculomotor nerve fibres = also autonomic motor (parasympathetic) for pupillary constrictor muscles + ciliary muscles (lens thickness)
What is the origin of the oculomotor nerves and trochlear nerves?
Midbrain
What is the origin of the abducens nerves?
Junction between pons/medulla
What are the 6 extraocular muscles of the eye, and the direction they pull?
Superior rectus
Inferior rectus
Medial rectus
Lateral rectus
Superior oblique
Inferior oblique
What is the formula for which cranial nerves control which extraocular muscles?
3(LR6SO4)
CN III controls all except…
CN VI controls lateral rectus
CN IV controls superior oblique
- CN III also controls upper eyelid muscle
What does damage to the oculomotor nerves result in?
Diplopia
Lateral strabismus (squint)
Dilated pupil from unopposed sympathetic stimulation
Dropping of upper eyelid
How can damage occur to the oculomotor nerves?
Stoke
Trauma to brainstem
What does damage to the trochlear nerves result in?
Vertical diplopia (affected eye drifts up)
Torsional diplopia
How can damage occur to the trochlear nerves?
Trauma to brainstem
What does damage to the abducens nerves result in?
Diplopia
Medial strabismus (squint)
How can damage occur to the abuducens nerves?
Has longest path in contact with bone of all CNs, may be easily compressed on bone from raised intercranial pressure
What is the general clinical test for the oculomotor, trochlear, and abducens nerves?
Follow end of pen/pen torch across visual fields
What is a clinical test specifically for the oculomotor nerves?
Shine torch into eye (pupillary light reflex)
What is the function of the trigeminal nerves?
Major sensory nerve to skin of face + underlying structures
What are the 3 major branches of the trigeminal nerves?
V1: Ophthalmic (sensory)
V2: Maxillary (sensory)
V3: Mandibular (sensory + motor to muscles of mastication)
What structure contains the cell bodies of sensory neurons (trigeminal nerve)?
Trigeminal ganglion
What does the ophthalmic branch of the trigeminal nerve receive sensory info from?
Skin of forehead (frontal branch)
Lateral upper eyelid (lacrimal branch)
Medial upper eyelid, tip of nose, part of nasal cavity, some sinuses (nasociliary branch)
What does the maxillary branch of the trigeminal nerve receive sensory info from?
Lower eyelids to the upper lip
Most of nasal cavity
Palates + upper teeth
Nasopharynx
What does the mandibular branch of the trigeminal nerve receive sensory info from?
Skin of lower lips and jaw
Lower teeth
Anterior 2/3 of tongue (general ie: touch, texture, pressure)
Floor of mouth
Which branches of the trigeminal nerves are most likely to damage speech?
Maxillary / mandibular
How can damage occur to the trigeminal nerves?
Facial injuries
Brain injuries
Pressure from blood vessels
What is the sensory clinical test for the trigeminal nerves?
Sharp-blunt test: pin with ball end and sharp end alternated
What is the motor clinical test for the mandibular branch of the trigeminal nerves?
Clench teeth / protrude jaw
What types of nerve fibres do the facial nerves carry?
Sensory
Motor
Autonomic: parasympathetic motor
What is the sensory function of the facial nerves?
Receives special sense taste sensation from ant 2/3 of tongue (chorda tympani)
What is the motor function of the facial nerves?
Motor to muscles of facial expression + lips
What is the autonomic function of the facial nerves?
Parasympathetic motor stimulation for
- salivary glands (sublingual
and submandibular)
- lacrimal glands
- nasal glands
What is the origin of the facial nerves?
Junction between pons/medulla
What are the 5 main branches (lower motor neurons) of the facial nerves
Temporal
Zygomatic
Buccal
Mandibular
Cervical
Why are the facial nerves important for speech and communication?
Movement of mouth + lips + facial expression
If a stroke occurred in the right corticobulbar tract, how would this impact the upper facial muscles and the lower facial muscles?
Upper facial muscles = bilateral weakness
Lower facial muscles = contralateral paralysis
What functions would be lost if there was damage to the facial nerves between the brainstem/middle ear?
All branches + functions lost
What functions would be lost if there was damage to the facial nerves after the middle ear?
Taste and lacrimation intact
Facial expression lost on that side
What functions would be lost if there was damage to the facial nerves on the face?
Individual muscle groups lost depending on branches damaged
What are 5 clinical tests for the facial nerves?
Inspect facial droop/asymmetry
Wrinkle forehead
Screw up eyes tightly
Purse lips & puff out cheeks
Stimulate taste on anterior 2/3 of tongue (must be quick so stimulus doesn’t diffuse across tongue)
What is the function of the vestibulocochlear nerves?
Special sense of hearing + balance
What types of nerve fibres are in the vestibulocochlear nerves?
Sensory only
Carries information from ears, info feeds into motor pathways (cerebellum), inputs back into vestibulospinal descending pathway for muscle adjustments
What is the origin of the vestibulocochlear nerves?
Medulla + pons
Which structure of the ear sends balance sensory info in the vestibulocochlear nerve?
Semicircular canals
Which structure of the ear sends sound sensory info in the vestibulocochlear nerve?
Cochlea
What are the 2 types of hearing loss, caused by damage to the ear/vestibulicochlear nerves?
Conductive hearing loss: from blockage or damage to outer/middle ear
Sensorineural hearing loss: damage to cochlea/CN VIII
What is the clinical test for the vestibulocochlear nerve?
High frequency turning fork, strike and hold 2cm from patient’s ear
- Can hear: hearing is fine
- Can only hear once fork on mastoid process: conductive hearing loss
- Cannot hear: sensorineural hearing loss
What are the 3 main sensory functions of the glossopharyngeal nerves?
- Sensory info from pharynx + posterior 1/3 of tongue
- Taste sensation from posterior 1/3 of tongue
- Visceral sensation from carotid sinuses and bodies (cardiovascular + respiratory reflexes)
What is the main motor function of the glossopharyngeal nerves?
Motor to stylopharyngeus muscle (forms lateral walls of pharynx)- swallowing
What is the main autonomic motor function of the glossopharyngeal nerves?
Parasympathetic secretomotor to activate parotid salivary glands
What is the origin of the glossopharyngeal nerves?
Medulla
How can damage to the glossopharyngeal nerves affect speech + swallowing?
Speech articulation issues: can indirectly affect speech clarity as nerve plays role in swallowing + pharyngeal function
Dysphagia: difficulties coordinating swallowing as stylopharyngeus muscle helps elevate pharynx during swallowing
How else (not SLT related) can damage the the glossopharyngeal nerves present?
Loss/alteration of taste sensation
Altered/absent gag reflex
What is the clinical test for the glossopharyngeal nerves?
Blunt object touches back of pharynx, should cause gag
What are the 3 main sensory functions of the vagus nerve?
- Somatosensory info from larynx
- Taste sensation from epiglottis
- Viscerosensory info from aortic bodies in aortic arch (sense blood chemistry) + general viscera (internal organs)
What is the main motor function of the vagus nerve?
Motor to soft palate + pharynx + larynx
What is the main autonomic function of the vagus nerve?
Parasympathetic to thorax + abdomen (eg: speeds digestion, slows HR)
Why can damage occur in many different places in the vagus nerves?
Has many ‘wandering’ branches
What does damage to the vagus nerves result in?
Loss of sensation from larynx
Loss of taste from epiglottis
Loss of autonomic functions
Loss of motor function to the soft palate, pharynx and larynx
If motor function to the soft palate is lost (vagus), what disorder can this lead to?
Dysarthria (difficulties with physical production of speech)
If motor function to the pharynx is lost (vagus), what disorder can this lead to?
Dysphagia (difficulties swallowing)
If motor function to the larynx is lost (vagus), what disorder can this lead to?
Dysphonia (difficulties with pitch/volume/quality of voice)
What are 2 clinical tests for the vagus nerves?
Say ‘ahh’, soft palate would elevate asymmetrically (weakness/paralysis to one side) and uvula would deviate to unaffected side
Patient should cough, weak/absent = damage to vagus
What is the function of the accessory nerves?
Controls muscles for certain movements of head + shoulders
What type of nerve fibres are in the accessory nerves?
Motor only
What is the origin of the accessory nerves
Upper cervical spinal cord
What muscles do the accessory nerves primarily innervate?
Sternocleidomastoid muscle: contraction tilts/rotates head to opposite side, both muscles flex neck forward
Trapezius muscle: shrugs + pulls shoulders
What does damage to the accessory nerves result in?
Weakness/paralysis
Head + neck + shoulder movement issues
Shoulder droop
Muscle atrophy
How can damage occur to the accessory nerves?
Surgical trauma eg: lymph node dissection/removal inadvertently damaging nerve
What is the clinical test for the accessory nerves?
Ask patients to turn head against resistance / shrug
What is the function of the hypoglossal nerves?
Moves tongue muscles
What type of nerve fibres are in the hypoglossal nerves?
Motor only
Descends ipsilaterally in corticobulbar tracts, and then crosses at medullary pyramids for contralateral innervation
What is the origin of the hypoglossal nerves?
Medulla, below pyramidal decussation
How can damage to the hypoglossal nerves affect speech and swallowing?
Articulation issues: difficulties with precise tongue shapes for speech sounds
Speech sound distortions: consonant sounds require intricate tongue movements
Dysarthria: slurred, unclear speech
Dysphagia: coordinating tongue movements swallowing, difficulties may manifest as chocking/aspiration
What is the clinical test for the hypoglossal nerves?
Protrude tongue, will deviate to injured side
→ due to unopposed action of contralateral intact muscles
What are the 4 functions of hearing?
Acquiring skills to speak clearly + effectively
Understand the speech of others
Respond to sounds necessary for survival
Appreciate natural + man-made sounds in our environment
How is the primary auditory cortex arranged?
Tonotopically
- neurons responding to low frequencies = anteromedial
- neurons responding to high frequencies = posterolateral
What does the secondary auditory cortex do?
Sound localisation
Analysis of complex sounds (eg: language)
Auditory memory
What is the overview for how sound is transmitted to the auditory complex?
Outer ear → middle ear → inner ear → brain
What structures are part of the outer ear? What are their function?
Auricle/pinna: collects + directs sound waves to ear canal
External acoustic/auditory meatus: transmits sound waves to tympanic membrane (ear drum)
What shape is the tympanic membrane?
Cone shape, catches + concentrates sound waves to tip
What are the 3 bones in the middle ear? What are their function?
Auditory ossicles
- malleus
- incus
- stapes
- carry sound vibrations from tympanic membrane to inner ear
What type of chamber is the middle ear?
Irregular chamber, air filled
How does the middle ear connect to the pharynx?
Air-filled Eustachian tube
note: common cause of ear infection → glue ear in children → affects speech production
What type of chamber is the inner ear?
Bony chamber, fluid filled
Where does the middle ear join the inner ear?
Oval window (stapes rests on oval window)
What structures do vibrations from the oval window travel through?
Fluid, which fills the cochlea + vestibule + semicircular canals
What structure in the inner ear detects sound?
Cochlea
What structure in the inner ear detects changes in head position for maintaining balance?
Vestibule
Semi-circular canals
How are nerve impulses sent in the inner ear?
Moving fluid activates tiny hairs on the end of the nerve cells which fires an action potential (mechanical activation of ion channels)
Then travel along vestibulocochlear nerve to brainstem
What are the 4 ways in which sound information from the inner ear needs to be interpreted?
Frequency (pitch)
Intensity (how loud)
Duration (how long)
Location (where is source)
What is the central auditory pathway for sound?
CNIII
Cochlear nuclei in medulla/pons junction
Superior olivary nuclei
Inferior colliculi nuclei
Thalamus
Auditory cortex
What happens to sound at the cochlear nuclei in the medulla?
Info from each each reaches the cochlear nuclei of the same side, half remains contralateral, half ipsilateral
What happens to sound at the superior olivary nuclei?
Each superior olivary nucleus compares the intensity + delay in sound from each ear, enables sound location accurate to 1º of an arc
By the inferior colliculi nuclei, how much auditory information is contralateral?
3/4
What are the important connections the inferior colliculi have with the superior colliculi relating to sound?
Nuclei controlling eye movement
Spinal cord controlling muscles of the neck
Spinal cord controlling postural muscles
- allow moving sound sources with the eyes/head/altering posture
What happens to sound at the thalamus?
Relay station sending incoming info to the whole cortex and to specific primary auditory complex to alert the brain of incoming info
Where is the final destination of auditory information?
Primary auditory cortex: transverse temporal gyri on superior surface of temporal lobe
How do auditory pathways differ to somatosensory pathways?
Auditory pathways cross and recross repeatedly
Several nuclei where synapses occur, and each plays a dif part in auditory function
What is the main function of the autonomic nervous system?
Regulates internal environment, maintains homeostasis
- not conscious, voluntary functions
What are 8 ways in which the ANS regulates the internal environment?
- Blood pressure, heart rate, airway diameter
- Gastrointestinal responses to food
- Focuses + dilating of eye
- Secretion of saliva + tears + sweat
- Adrenaline release
- Thermoregulation
- Urinary bladder regulation
- Sexual function
What is another name for the sympathetic branch? (think about where sympathetic nerves exit from)
Thoracolumbar part
What is another name for the parasympathetic branch? (think about where parasympathetic nerves exit from)
Craniosacral part
What is the ANS pathway?
Emotional input
Starts in hypothalamus
Travels down fibres in lateral spinal cord OR activates cranial nerves
What is the 2-step pathway for AUTONOMIC NS lower motor neurons after they emerge from the spinal cord?
Always a pre-ganglionic neuron and a post-ganglionic neuron that synapses in a ganglion
What are the 3 differences between the parasympathetic and the sympathetic nervous system?
Point of exit from the CNS
Length of pre and post ganglionic neurons
Type of neurotransmitter
How does the point of exit from the CNS differ between the sympathetic and parasympathetic nervous system?
Sympathetic nerves emerge alongside T1-T12 and L1-L3 spinal nerves
Parasympathetic nerves emerge from brainstem cranial nerves III VII IX X and S2-S4 spinal nerves
How does the length of pre and post ganglionic neurons differ between the sympathetic and parasympathetic nervous system?
Sympathetic = short pre-ganglionic, long post- ganglionic
Parasympathetic = long pre-ganglionic, short post-ganglionic
How does the type of neurotransmitter differ between the sympathetic and parasympathetic nervous system?
Sympathetic…
- 1st synapse: acetylcholine
- 2nd synapse: noradrenaline
Parasympathetic:
- 1st synapse: acetylcholine
- 2nd synapse: acetylcholine
What are 3 effects of the sympathetic nervous system on the cardiovascular system?
Increases heart rate
- Dilates blood vessels in muscle
- Constricts blood vessels in skin and GIT
What is the effect of the parasympathetic nervous system on the cardiovascular system?
Decreased heart rate
- note blood vessels don’t need parasymp supply, no relaxer nerves, naturally dilates when symp constriction eases
What is the effect of the sympathetic nervous system on the respiratory system?
Dilates bronchial tree + pulmonary blood vessels (increases gas exchange)
What is the effect of the parasympathetic nervous system on the respiratory system?
Constricts bronchial tree + pulmonary blood vessels to normal diameters
What are 5 effects of the sympathetic nervous system on the gastrointestinal tract?
Inhibits secretion
Inhibits motility
Constricts blood vessels to the gut
Butterflies, GI disturbance
Less saliva, dry mouth
What are 3 effects of the parasympathetic nervous system on the gastrointestinal tract?
Stimulates secretion of more saliva for eating
Stimulates motility of gut
Blood vessels dilate when symp tone is decreased
What are 5 effects of the sympathetic nervous system on the skin?
Constricts blood vessels (pale)
Stimulates sweat secretion
Hair erection
note: no parasymp supply, just returns to normal when symp stimulation stops
What are 2 effects of the sympathetic nervous system on the eye?
Pupil dilates
Inhibits lacrimal gland secretion
What are 3 effects of the parasympathetic nervous system on the eye?
Pupil constricts
Increased thickness of lens for accommodation
Stimulates lacrimal secretion (tears)
What is the limbic system?
One of the oldest parts of the brain
Areas in the cortex surrounding the diencephalon
- dif areas are connected, forming complex communication loops
What is the limbic system involved in? Why is it important?
Involved in cognitive functions (memory, attention, emotional responses)
Important as it controls many of the responses mediated by the ANS (makes sense of situations and activates/inhibits apt ANS response)
What are 3 important regions of the limbic system for the ANS?
Amygdala
Hippocampus
Hypothalamus
What does the amygdala control?
Emotional excitability- assesses sensory inputs for emotional significance and triggers response
What does the hippocampus control?
Contextual processing of experience (particularly stress)
Converts ST memories to LT
Spatial navigation
What does the hypothalamus control (think limbic system + ANS)?
Integrates inputs, coordinating ANS activation of symp OR parasymp, adapts to emptional + environmental demands
Can activate adrenal medulla to release adrenaline + noradrenaline
