Topic 4 - The Nervous System Flashcards
What are the two main branches which the nervous system is divided into?
- Central nervous system
* Peripheral nervous system
What are the components of the CNS (central nervous system)?
- Brain
* Spinal cord
What are the components of the PNS (peripheral nervous system)?
Everything which lies outside of the brain and spinal cord
What are afferent pathways?
Nerve pathways which carry sensory information towards the brain from the periphery
What are efferent pathways?
Nerve fibres which carry motor information from the brain to the periphery
How many planes of the body are there?
3
What are the names of the planes of the body?
- Saggital
- Coronal
- Transverse
What is the saggital plane (of the body)?
A vertical line which divides the body into a left and right section
What is the transverse plane (of the body)?
A horizontal line which divides the body into upper and lower sections
What is the coronal plane (of the body)?
A vertical line which divides the body into anterior (front) and posterier (back) sections
What are the upper and lower sections of the body called?
- Superior
* Inferior
What are the terms for the front and back sections of the body?
- Anterior
* Posterior
What are the three sections the brain is broadly divided in to?
- Cerebrum
- Cerebellum
- Brainstem
What is the cerebrum?
The largest part of the brain
What are some of the particularly important subregions of the cerebrum?
- Basal ganglia
- Amygdala
- Thalamus
- Hippocampus
Where is the cerebellum?
Located at the back of, and below, the cerebral hemispheres
What is the cerebellum concerned with?
- Organisation of balance
- Posture/locomotion
- Fine motor control
- Attention
- Time perception
Where is the brainstem located?
Anteriorly to the cerebellum
What does the brainstem contain?
- The midbrain
- The pons
- The medulla oblongata
What does the brainstem do?
It communicates with the peripheral nervous system to control involuntary processes such as breathing and heart rate
What are the deep ridges of the brain called?
Gyri (singular, gyrus)
What are the grooves of the brain called?
Sulci (singular, sulcus)
What are deep sulci (grooves of the brain) known as?
Fissures
What are the names of the three layers of meninges that cover the brain and spinal cord?
- Dura mater
- Arachnoid mater
- Pia mater
What is the corpus callosum?
A broad, myelinated bundle of nerve fibres which connects the two cerebral hemispheres of the brain
What are the four lobes of the cerebral cortex?
- Frontal lobe
- Occipital lobe
- Parietal lobe
- Temporal lobe
What is the occipital lobe responsible for?
Processing visual information
What is the temporal lobe responsible for?
- Interpreting speech / hearing
- Olfaction
- Learning / memory
- Emotion
What is the parietal lobe responsible for?
- Body orientation
- Interpretation of somatosensory information
- Taste
What is the frontal lobe responsible for?
- Higher cognitive thought
- Memory
- Control of voluntary movement
What does the hypothalamus control?
- Certain metabolic processes and autonomic activities
- Body temperature
- Hunger
- Thirst
- Involved with emotion
What does the thalamus control?
Relaying sensory input from the peripheral nervous system to the cerebral cortex
What does the amygdala control?
It is connected with the limbic system (which controls motivation-driven behaviours)
What does the hippocampus control?
- Motivation
- Emotion
- Formation of memories
What does the basal ganglia control?
Movement
What is the limbic system?
A system of functionally regulated structures in the brain which are involved with emotion and motivation-driven behaviours
Damage to which subcortical regions would cause memory problems?
- Hypothalamus
* Hippocampus
Damage to which subcortical regions would cause difficulty processing emotions?
- Hypothalamus
- Amygdala
- Hippocampus
- Thalamus
What are the four divisions of the spinal cord?
- Cervical
- Thoracic
- Lumbar
- Sacral
What systems is the autonomic nervous system further subdivided in to?
- Enteric nervous system
- Sympathetic nervous system
- Parasympathetic nervous system
What is the enteric nervous system responsible for?
- Communicating information about chemical changes and movement within the digestive system to the brain
- Coordinating the release of digestive hormones
- Muscle contraction of the digestive tract
Which nervous system would be activated in response to a stressful event?
The sympathetic nervous system
What is the dorsal root?
The neuronal pathway which carries sensory information from the periphery to the spinal cord
What is the ventral root?
The neuronal pathway which carries information from the brain to the spinal cord
What are reflex arcs?
Circuitry within the nervous system which is responsible for simple reflex actions
What is the name for the part of a neuron which receives information from other cells?
Dendrite
What is the purpose of myelin?
To enhance the speed with which a signal can move along the axon
What are areas of the brain which contain bundles of axons (nerve fibres) called?
White matter
What are regions of unmyelinated cell bodies referred to as?
Grey matter
How much of the body mass does the brain account for?
How much of the body’s energy requirements does it use?
- Only 2%
* Around 20%
What type of junctions do the endothelial cells of the brain create?
Tight junctions
What is the purpose of CSF (cerebrospinal fluid)?
To cushion the brain and protect the spinal cord from trauma
Roughly how much circulating CSF (cerebrospinal fluid) does an adult have?
About 80 - 150ml
What are the main components of CSF (cerebrospinal fluid)?
- Glucose
- Proteins
- Waste substances such as lactic acid and urea
- Cations
- Anions
- Possibly white blood cells
What are the ventricles of the brain?
Cavities within the brain which are filled with CSF (cerebrospinal fluid)
Where are the lateral ventricles in the brain?
One is in each cerebral hemisphere, each under the corpus callosum
What is the choroid plexus?
A network of blood vessels and epithelial cells found in the ventricles of the brain which produce CSF
What is CSF (cerebrospinal fluid) mainly derived from?
Filtered blood
What is the resting potential of a neuron?
-70 mV
What happens to the resting potential of a neuron when sodium ions enter it?
The potential becomes less negative, and increases to -50 mV
What is an action potential?
A coordinated change in the membrane potential that travels along the axon as a wave of electricity. It is commonly referred to as a nerve impulse
Which ion is principally associated with neuronal depolarisation and repolarisation?
- Sodium ions moving in to the neuron cause depolarisation
* Potassium ions moving out of the neuron cause repolarisation
What are the nodes of Ranvier?
Small gaps in the myelin where ions move across the axon membrane during an action potential
What is saltatory conduction?
The process by which, if myelin is present on an axon, the nerve impulse that is conducted will “jump” from node to node in the myelin layer
What is a synapse?
The junction between two neurons, or between a neuron and a muscle cell, which allows for the transfer of messages from one cell to another using neurotransmitters
What is a neurotransmitter?
A chemical substance released from the terminal ending of an axon into a synaptic cleft during the transmission of a nerve impulse, which relays information from one neuron to another (across a synapse)
What are some of the common compounds which can act as neurotransmitters?
- GABA
- Serotonin
- Adrenalin
- Acetylcholine
- Noradrenaline
- Glutamate
- Dopamine
- Glycine
What are excitatory neurotransmitters?
Neurotransmitters which increase the likelihood that a neuron will fire an action potential
What are inhibitory neurotransmitters?
Neurotransmitters which decrease the likelihood that a neuron will fire an action potential
What is summation (re neurons)?
The process by which a neuron “sums up” all the excitatory and inhibitory signals it has received over a period of time
What is amyloid precursor protein (APP)?
A protein which is processed by secretase enzymes to produce the amyloid-Beta peptide
What is amyloid-Beta?
A peptide which aggregates in the brain in Alzheimer’s disease
What happens if levels of amyloid-Beta build up in the brain?
They cause synaptic dysfunction which impairs neuronal communication, which eventually causes neurons to die
What is meant by the medical term ‘incidence’?
The number of new cases diagnosed in a population over a given time
What is meant by the medical term ‘prevalence’?
The total number of cases in the population at a given time
How many cranial nerve pairs are there which arise directly from the brain?
12
Taste buds are embedded in epithelium which forms structures called what?
Papillae
What are papillae (re the tongue)?
Specialised epithelial cells on the tongue’s surface which house chemical-sensitive taste buds
What type of taste are fungiform papillae sensitive to?
- Sweet
- Salt
- Sour
What type of taste are foliate papillae sensitive to?
Bitter
What type of taste are circumvallate papilllae sensitive to?
Bitter
What type of taste are filiform papillae sensitive to?
They do not house taste buds! They are used to create friction and grip and detect food texture
Which ions bind to taste receptors in order for us to detect sour tastes?
Hydrogen ions
Which ions bind to taste receptors in order for us to detect salty tastes?
Metal ions, e.g. sodium and potassium
What does the ability to taste sweet things come from?
The ability to detect sugars (both naturally occuring and artificial)
Signals sent to which parts of the brain are involved in the perception of taste?
- The primary gustatory cortex (frontal lobe)
* The thalamus
What are the components of the outer ear?
- The auricle (ear lobe)
* The auditory canal
What are the components of the middle ear?
- Tympanic membrane
- Malleus
- Incus
- Stapes
What are the components of the inner ear?
- Bony labyrinth
- Scala vestibuli
- Scala tympani
- Scala media
Which are the specialised language centres of the brain that process sounds associated with speech?
- Wernicke’s area
* Broca’s area
What are the three categories which touch sensations can be divided in to?
- Mechanoreception
- Thermosensation
- Nociception
What is mechanoreception (re touch)?
Sensory receptors which produce action potentials in sensory neurons as a result of a deformation of their cell membrane, including touch receptors and hair cells
What is thermosensation (re touch)?
Sensory information about temperature
What is nociception (re touch)?
Pain that occurs in response to physical injury to the body tissues, where body tissues does not include nerves
What are “Meissner’s corpuscles” (re skin)?
Where are they found?
- Also called tactile corpuscles, they are egg-shaped encapsulated masses of dendrites
- Located in hairless skin, and abundantly in hands, feet, lips, external genitalia
What are “Pacinian corpuscles” (re skin)?
Where are they found?
- Large oval structures consisting of a dendrite wrapped in a multilayered, connective tissue capsule. They are involved in sensing pressure
- Throughout the body, in the dermis, subcutaneous and deeper regions (e.g. muscles)
What are “Merkel’s discs” (re skin)?
Where are they found?
- They are slow adapting touch receptors. Flattened, saucer-shaped free nerve endings which connect to Merkel cells
- Abundantly in fingertips, hands, lips, external genitals
What are “Ruffini’s corpuscles” (re skin)?
Where are they found?
- Elongated, encapsulated receptors which respond to stretching, often associated with the movement of limbs
- The dermis; hands and soles of feet
What do Meissner’s corpuscles detect?
- Light touch
- Changes in stimulus
- They give the sensation of touch, pressure and vibration
What do Pacinian corpuscles detect?
- High-frequency vibrations
* They give the sensation of pressure
What do Merkel’s disks detect?
They give the sensation of pressure for as long as the stimulus is present
What do Ruffini’s corpuscles detect?
Stretching movement which is caused by a limb or digit
How are sensations of cold and heat relayed to the brain?
Via afferent pathways which are activated by transient receptor potential (TRP) ion channels
How many transient receptor potential (TRP) ion channels have been discovered in humans?
28
What is special about a-delta nerve fibres?
They are lightly myelinated
Are C (nerve) fibres myelinated?
No
What type of sensations are a-delta (nerve) fibres predominantly sensitive to?
- Heat
* Mechanical
What type of sensations are C (nerve) fibres) sensitive to?
- Thermal
- Mechanical
- Chemical
Which type of nerve fibre conducts information about pain faster, a-delta or C fibres?
A-delta
What is proprioception?
The ability to sense the location, position, orientation and movement of the body and its parts in space
What are “rapidly adapting” (nerve) receptors?
Ones which respond maximally when a stimulus is first presented, but then ‘adapt’ to the sensation and stop firing, even if the stimulus remains
What are “slowly adaptin” (nerve) receptors?
Once which will fire for as long as the stimulus is present
What is the dorsal column-medial lemniscus pathway?
The pathway which ascends the spinal cord and is responsible for relaying tactile information, joint position and vibration to the brain
What is the spinothalmic (anterolateral) pathway?
Nerve fibres which ascend towards the brain and relay sensory information from the periphery regarding heat and pain
A larger part of the cortex is dedicated to processing information from which body parts?
- Face
- Lips
- Tongue
What are the main wavelengths of the electromagnetic spectrum?
- Gamma rays
- X-rays
- Ultraviolet
- Visible
- Infrared
- Microwaves
- Radio waves
What is the range of wavelengths which are visible to the human eye?
From 380 nm to 780 nm
Which part of the nervous system is responsible for controlling the size of the iris?
The autonomic nervous system
What are the two types of photoreceptors we have in our eyes?
- Cones
* Rods
Which type of vision are cones responsible for detecting?
- Detail
* Colour
What are rods sensitive to?
Low levels of light
From anterior to posterior, what is the order of the pathway by which visual information is communicated from the eye to the brain?
- Optic nerve
- Optic chiasm
- Optic tract
- Thalamus
- Primary visual cortex
Where are the visual association cortices in the brain?
- Occipital lobe
- Temporal lobe
- Parietal lobe
Where do the optic nerve fibres synapse within the brain?
- The midbrain
- The hypothalamus
- The thalamus
What bodily functions does the ANS (autonomic nervous system) control?
- Respiration
- Cardiovascular functions
- Glandular functions
- Digestion
What functions does the PNS (parasympathetic nervous system) perform?
- Accelerate heart rate/increase blood pressure/constrict vessels
- Dilate pupils
- Dilate bronchial passages
- Decrease large intestinal motility
- Increase oesophageal peristalsis
What are astrocytes?
Small, star-shaped cells which provide support for brain homeostasis and neuronal metabolism
What are microglia?
Immune cells which survey the CNS and respond to any signs of infection or damage
What are oligodendrocytes?
Cells which form myelin
Where does the olfactory nerve originate?
The olfactory bulb
Where does the optic nerve originate?
The retina
What does the trochlear nerve connect to?
Other eye muscles
Where does the trigeminal nerve go to/from?
- To: jaw muscles, tympanic membrane
* From: face, nose
Where does the abducent cranial nerve travel to?
External eye muscles
Where does the vestibiocochlear nerve originate?
The inner ear
Where does the glossopharyngeal nerve travel to/from?
- To: pharyngeal muscles
* From: heart, lungs, abdomen, external ear
Where does the accessory nerve travel to?
Neck muscles
Where does the hypoglossal nerve originate?
Tongue muscles
What do glial cells do?
- Bring nutrients to neurons
- Insulate parts of neurons
- Digest parts of dead neurons
