Anatomy & Physiology Flashcards
What are muscles responsible for?
- movement
- heat production
- posture
What are the characteristics of skeletal muscle tissue?
- excitability: stimulated
- contractility: contract/shorten
- extensibility: stretch/extend (muscles return to ‘resting’ length)
3 Types of Muscle Tissue
1) skeletal
2) cardiac
3) smooth
What is another name for skeletal muscle?
- striated
- voluntary
How much of body weight is skeletal muscle?
40%-50%
Skeletal Muscle
- attached to bone
- microscopic striations
- voluntary contractions
- multiple nucleus’ (on periphery of cell)
4 Parts of a Skeletal Muscle Cell
1) cells = fibres (threadlike)
2) plasma membrane = sarcolemma
3) cytoplasm = sarcoplasm
4) endoplasmic reticulum = sarcoplasmic reticulum (SR), calcium release and storage
What do muscle fibres contain?
- many mitochondria, nuclei and myofibrils
- T Tubules
T Tubules
- inward extensions of the sarcolemma
- allow nerve impulses to move deeper into the fibre
Myofibrils
-numerous fine fibres packed close together in the sarcomere
What are myofibrils made of?
-myofilaments (fine, threadlike structures)
How many types of protein make up myofilaments?
4
Myosin
-makes up thick myofilaments
Actin
-makes up thin myofilaments
Sarcomere
-repeating segments of actin and myosin
What is the basic functional unit of muscle fibres?
sarcomere
How are individual sarcomeres separated?
-z lines (disks)
Neuromuscular Junction
-microscopic ‘gap’ called the synapse, between the end of the motor neurone and the sacrlemma
When will a skeletal muscle stay at rest until?
-it is stimulated by a nerve impulse, which arrives via a motor neurons
The nerve impulse travels along the motor neurone until it reaches the…
neuromuscular junction
How are neurotransmitters released?
nerve impulses are transmitted across the synapse
Where do neurotransmitters and receptors bind?
sarcolemma
What happens when the neurotransmitters bind with the receptors at the sarcolemma?
trigger the SR to release Ca++ into the sarcoplasm
What plays a role in the binding of myosin and actin?
the Ca++ released by the SR
What happens between myosin and actin during contraction?
- form ‘cross bridges’
- act as levers to pull myofilaments past each other
What happens as a muscle contracts?
-myofilaments slide past eachother
What does contraction require?
- calcium (cross bridge)
- ATP (for energy)
How do you stop contraction?
-SR actively removes Ca++
Aerobic
- occurs when oxygen levels are normal
- supplies energy for long periods of time
- example: walking
Anaerobic
- occurs when oxygen levels are low
- fast process
- supplies energy for a few mins of maximal exercise
- example: 100m sprint
What does anaerobic activity result in?
-production of lactic acid and lack of oxygen (since oxygen is required to convert lactic acid back into glucose)
What produces lactic acid?
- contraction when there is not enough oxygen
- results in muscle soreness
Why do we breathe heavily after exercise?
-to make up for oxygen debt
What does fatigue lead to?
- reduced strength
- loss of muscle’s ability to contract
- depletes cellular ATP store
Where does energy for contraction come from?
-breaking ATP bonds
Motor Neuron
-specialized nerve fibre that transmits an impulse to a muscle, causing contraction
Neuromuscular Junction
-specialized point of contact between a nerve ending and a muscle fibre
Motor Unit
a motor neuron + the muscle cell it innervates
How does the number of fibres in a motor unit affect it?
- fewer fibres: more precise
- more fibres: more powerful
Neurotransmitters
- released by the motor neurone in response to a nerve impulse
- start actions inside the muscle fibre that initiate contraction
5 Types of Muscle Contractions
- twitch
- tetanic
- tonic
- isotonic
- isometric
Myography
-method of graphing the changing tension of muscle as it contracts
Twitch Contractions
- quick, jerky response to stimulus
- ‘lab phenomena’ (not related to normal muscle activity)
- in isolated muscle fibres
Tetanic Contraction
- sustained and steady
- caused by a series of stimuli bombarding a muscle in rapid succession
- this series of stimuli ‘join forces’ to produce a sustained/prolonged contraction (tetanus)
- calcium dependant
- example: lock jaw
Tonic Contraction
- continual and partial
- at any time, a few muscle fibres are contracting
How is muscle tone maintained?
negative feedback
Flaccid
muscles have less tone than normal
Spastic
muscles have more tone than normal
What does the strength and time of skeletal muscle contraction depend on?
- metabolic condition
- number of fibres contracting
- number of motor units involved
- intensity
- frequency
What is a muscles maximum strength dependant on?
-initial length of its fibres (the longer, the more they contract/shorten)
What happens to a skeletal muscle if the sarcomeres are compressed?
-reduces the muscles ability to compress
What happens if sarcomeres are overstretched?
-actin and myosin are too far apart to bind
When does the strongest muscle contraction occur?
-when the muscle is stretched to its optimal length
Isotonic Contractions
- produces movement at a joint
- muscle changes length
- tension stays the same
Concenteric Contraction
- muscle shortens as it contracts
- insertion end of muscle moves toward the origin
Eccenetric Contraction
- muscle lengthens while contracting
- produces tension
- insertion moves away from point of origin
Most types of body movements are…
isotonic contractions
Isometric Contractions
- tension within muscle increases, but muscle doesn’t shorten (no movement)
- example: pushing against a wall
- muscle length is the same contracted or relaxed
What are repeated isometric contractions cause?
stronger muscles
Effects of Exercise on Skeletal Muscles
- improves muscle tone
- improves posture
- better heart and lung function
- reduces fatigue
- develops muscle tissue
- maintain healthy weight
What causes atrophy?
-long periods of time without activity
What causes hypertrophy?
-regular exercise
What do exercises such as weight lifting, squats and planking (strength training) do to skeletal muscles?
- increases number of myofilaments in each muscle fibre
- increases total mass of muscle
- does NOT increase number of muscle fibres
What do endurance exercises (aerobic training) do for skeletal muscles?
- allows more efficient delivery of oxygen and nutrients to a muscle (increased blood flow)
- increase the number of mitochondria in muscle
- does NOT result in muscle hypertrophy
Cardiac Muscle
- composes bulk of heart
- loaded with mitochondria
- doesn’t run low on mitochondria
- no fatigue
Intercalated Disks
- dark bands that join branches of cells
- enables heart to contract
Are cardiac muscles voluntary of involuntary?
involuntary
Do cardiac muscles have more than one nucleus?
Yes, many nuclei are centrally located.
Smooth Muscle
- myofibrils not organized into sarcomeres
- walls of hollow visceral structures (digestive tract, blood vessels, ureters)
- single unit and multi unit
Smooth muscles are also called…
- non striated
- involuntary
- visceral
Do smooth muscles have more than one nucleus?
No, they have one, centrally located nucleus.
What does muscle function depend on?
- bones and joints
- respiratory, circulatory, nervous, and skeletal systems
What is the nervous system made up of?
- brain
- spinal cord
- nerves: cranial and spinal
What 2 parts is the nervous system divided into?
- CNS
- PNS
CNS
- brain and spinal cord
- ‘centrally located’
- structural and functional centre of the entire nervous system
- control centre: interprets incoming (sensory) info and sends out a response
PNS
- nerves that extend to ‘peripheral’ parts of the body (from the brain and spinal cord)
- communication network between CNS and the rest of the body
Afferent Division
- INCOMING sensory pathways
- sensory info from visceral effectors to CNS
Efferent Division
- OUTGOING motor pathways
- motor info from CNS to visceral effectors
Somatic
-communication between CNS and skeletal muscles
Autonomic
-communication between CNS and ‘visceral effectors’ (smooth muscles, cardiac muscles, glands, adipose, etc)
Sympathetic
- fight or flight
- stress response activities
Parasympathetic
- rest and repair
- normal resting activities
What are the 2 subdivisions of the PNS?
- automatic NS
- somatic NS
Automatic Nervous System (ANS)
- involuntary
- visceral motor nerves
- impulses from CNS to cardiac muscles, smooth muscles and glands
Somatic Nervous System (SNS)
- voluntary
- somatic motor nerves
- impulses from CNS to skeletal muscle
What are the 2 types of cells in the NS?
- glia/neuroglia (supporting)
- neurons (nerve cells)
Glia
- provide support and protection for NS
- regulate function and structure of neurons
- do NOT transmit nerve impulses
- 5x more abundant than neurons
What are the 5 major types of glia/neuroglia?
1) astrocytes (CNS)
2) microglia (CNS)
3) ependymal cells (CNS)
4) oligodendrocytes (CNS)
5) schwann cells (PNS)
Astrocytes
- bigger than glia
- transfer nutrients from blood to neurons
- part of the BBB
What does the BBB do?
- separates blood from brain tissue
- protects brain from harmful substances that may be in blood
Microglia
- smaller than astrocytes
- first/main form of immune defence for brain and spinal cord
- usually stationary, but can move
- act as phagocytes
Macrophages
- phagocytes
- decrease inflammation
- destroy harmful substance to prevent damage to CNS tissue
Ependymal Cells
- resemble epithelial cells
- form thin sheets that line fluid filled cavities in CNS
- produce fluid
- aid in circulation of fluid
Oligodendrocytes/oligodendroglia
- extends branches to the axon of neurons to hold them together
- can wrap around more than 50 axons
- form the myelin sheath
Myelin Sheath
- fatty substance that electrically insulates axons
- essential for function of nervous system
Schwann Cells
- support nerve fibres
- similar to oligonderocytes of CNS
- wrap around the axon of the neuron
Myelin
- fatty substance around axons of neuron (CNS and PNS)
- insulator
What are unmyelinated spaces called?
- nodes of Ranvier
- electrical activity
- allows for rapid transmission of nerve impulse
What forms myelin in the CNS?
oligodendroglia
What forms myelin in the PNS?
Schwann cells
Saltatory Conduction
-rapid, effective transmission of a nerve impulse
Neruons
- structural and functional units of NS
- initiate and conduct impulses that make NS functions possible
What are the 3 main parts of a neuron?
- dentrites
- cell body (contains organelles)
- axon
Dendrites
- branching projections
- conduct impulses to cell body
Cell Body
-main part
-contains nucleus and organelles
found in CNS
Axon
- long, single protection from cell body
- sometimes myelinated
- distal tips terminate in a ‘synaptic knob’
What are the 3 types of neurons?
- sensory neurons/afferent neurons
- motor neurons/efferent neurons
- interneurons/ central neurons/connecting neurons
Sensory/Afferent Neurons
- sense stimuli
- impulses from receptors all over the body, and send to brain and spinal cord
Motor or Efferent Neurons
-impulses away from brain and spinal cord to muscles and glands
Interneurons (aka. central or connecting neurons)
-impulses from sensory neurons to motor neurons
What is another name for nerve impulses?
-action potential
What is a reflex arc?
-specialized neurone pathway that results in rapid involuntary or autonomic response to stimulus
What are the 2 types of reflex responses?
- contraction by a muscle
- secretion by a gland
Does a particular stimulus always cause the same reflex?
Yes.
What are 5 components to a reflex arc?
1) receptor-detects change & generates nerve impulse
2) sensory/afferent neuron-transmits impulse to CNS
3) CNS-integrating centre with one or more synapses (where interneurons are located)
4) motor/efferent neuron-transmits impulses from CNs to effector
5) effector-muscle or gland that performs the action
What are the 2 types of reflex arcs?
- 2 neuron arcs
- 3 neuron arcs
2 neuron arcs
- simplest reflex arc
- consist of sensory neurons synapsing in the spinal cord with motor neurons
- no interneuron
3 neuron arcs
- sensory neurons, motor neurons, interneurons
- associated with more complex responses, such as response to injury/pain (withdrawal reflex)
- provide automatic reactions that must occur quickly (survival)
2 neuron arcs
- sensory neurons, motor neurons
- simple, ‘unlearned’ reflexes
- used to make sure NS is working properly (pupil dilation)
Where are interneurons located?
-grey matter of brain or spinal cord
Nerve
- bundles of peripheral nerve fibres held together by layers of connective tissue
- covered by myelin sheath
- appear white
Mixed Nerves
- contain sensory and motor neurons
- sensory nerves are mostly sensory neurons
- motor nerves are mostly motor neurons
White Matter
-tissue composed of myelinated axons
Grey Matter
-tissue composed primarily of cell bodies and unmyelinated fibres
Nerve Coverings
-individual axons (nerve fibres), fascicles and nerves are surrounded by thin layers of fibrous connective tissue that have specific names
What are the 3 nerve coverings?
1) endoneurium
2) perineurium
3) epineurium
Endoneurium
- endo=within/inside
- surrounds individual nerve fibres/axons
Perineurium
- peri=around
- surrounds individual fascicles (bundle of fibres/axons) of nerves
Epineurium
- epi=upon
- surrounds numerous fascicles and blood vessels to form a complete nerve
Tracts
- bundle of nerve fibres/axons in CNS
- no CT covering
White Matter
- PNS: myelinated nerves
- CNS: myelinated tracts
Grey Matter
- unmyelinated cell bodies and nerve fibres
- PNS: ganglia
- CNS: nuclei
Single axons are also called…
nerve fibres
A bundle of axons in the PNS is called a…
fascicle
A bundle of fascicles in the PNS is called a…
nerve
A bundle of axons in the CNS is called a…
tract
Nerve tissues made up of primarily myelinated fibres is called…
white matter
Nerve tissue made up primarily of unmyelinated fibres is called
grey matter
Why is nerve damage permanent?
- mature nervous are incapable of cell division
- neurons have limited capacity to repair themselves
When might nerve fibres repair themselves?
-mild damage
-cell body and neurilemma are intact
no scarring
What is a nerve impulse?
a self-propagating wave of electrical disturbance that travels along the surface of a neuron’s plasma membrane
Membrane Potential
-difference in electrical charge across a membrane (positive on outside, negative on inside)
A membrane that exhibits a membrane potential is said to be ______.
polarized
Resting Membrane Potentials
- is not conducting electrical signals
- excess of positive ions on outside
- plasma membrane contains channels (called sodium-potassium pumps) that allow Na+ and K+ across it (in opposite directions and at different rates)
- movement maintains electrical different on plasma membrane
Local Potential
- fluctuation in resting potential in plasma membrane
- occurs in response to stimuli (excitation)
- excitation triggers opening of ‘stimulus gates channels’ in plasma membrane allows more Na+ to enter neuron (charge in now more negative on outside)
- more Na+ means the size of membrane potential is reduced (depolarization)
- initiates action potential
What marks the beginning of a nerve impulse/action potential?
inward movement of Na+, leaving a temporary, slight excess of negative ions on the outside of the membrane
Saltatory Conduction
-a nerve impulse jumping over myelin covered areas
Synapse
-microscopic junction between neurons
Electrical Synapse
-occur where cells joined by a gap junction allows potential to continue along postsynaptic membrane
Chemical Synapse
-occur where presynaptic cells release chemical transmitters (neurotransmitters) across a tiny gap to the postsynaptic cell
What are the 2 kinds of synapse?
- chemical
- electrical
What 3 structures is the synapse composed of?
- synaptic knob
- synaptic cleft
- plasma membrane of postsynaptic neuron
what does a synapse ensure?
that there is only one way transmission of nerve impulses
What does a plasma membrane of a postsynaptic neuron contain?
receptor for neurotransmitters
Synaptic Knob
- tiny bulge of a terminal branch of a presynaptic neuron’s axon (aka axon terminal)
- contains vesicles full of neurotransmitters
Synaptic Cleft
-microscopic space between synaptic know and plasma membrane of postsynaptic neuron (at dendrites)
How many compounds are known to be neurotransmitters?
over 50
What do compounds that are neurotransmitters do?
assist, stimulate (excitatory) or inhibit (inhibitory) postsynaptic neurons
What are the major compounds known to be neurotransmitters?
- acetycholine (ACh)
- catecholamines
- endorphins and enkephalins
Acetycholine
-neurotransmitter of autonomic nervous system
Catecholamines
- noradrenaline/norepinephrine, adrenaline/epinephrine, dopamine, serotonin
- sleep, mood, pleasure recognition, motor function
Endorphins and Enkephalins
- morphine like
- natural pain killers
Organs of the Nervous System
- brain
- spinal cord
- nerves: cranial and spinal
- sensory organs: eyes, ears, specialized sensory organs
- free nerve endings in skin
What are the 2 parts of the CNS?
- brain
- spinal cord
What protects the CNS?
- skeletal system
- integumentary system
- cranial bone and vertebrae
- meninges
Meninges
- tube like covering of spinal cord
- lines vertebral foramen
- extend across brain and enclose it
What are the 3 membranous layers o meninges?
1) dura- outer layer, strong, white fibre, lines vertebral canal, inner periosteum of cranial bones
2) arachnoid-middle layer, cushioning, CSF in spaces
3) pia mater- innermost layer, surface of brain and spinal cord, forms delicate hilum terminale
Epidural Space
- immediately outside of dura
- inside vertebrae or skull
Subdural Space
- between dura and arachnoid
- contains serous fluid
Subarachnoid Space
- between arachnoid and pis
- contains CSF
Functions of CSF
- protects brain and spinal cord
- supplies nutrients to tissue of CNS
- acts as the CNS lymphatic system: removes waste, provides immunilogical protection to CNS tissue
Where is CSF found?
- subarachnoid space
- within canals and cavities
What are the 4 fluid filled spaces in the brain called?
ventricles
How is CSF formed?
- continually
- forms fluid/plasma filtering out of blood at capillary networks projecting from pia into the lateral 3rd and 4th ventricles (choroid plexuses)
- this fluid then enters the ventricles of the brain and is called CSF
Arachnoid Villi
-absorbs CSF through ventricles and subarachnoid space back into the blood
How much CSF is there and how often is it replaced?
- 150mL
- replaced ever 3 to 4 hrs
What is hydrocephalus?
-blockage and accumulation of CSF
How long is the spinal cord?
17-18 inches
What part of the CNS is most susceptible to injury?
spinal cavity
Where does the spinal cavity extend from?
foramen magnum (L1)
Where are the 2 bulges of the spinal cord?
- cervical region
- lumbar region
Dorsal Root of Spinal Cord
- bundles of fibres that carry sensory info into spinal cord
- contains dorsal root ganglia (grouping of unmyelinated cell bodies of the sensory neurons)
Ventral Root
-bundles of nerve fibres that carry motor info out of spinal cord
Dorsal and ventral roots join to form…
spinal nerves
Funiculi
3 areas of spinal cord
- anterior
- posterior
- lateral
_____ matter surrounds _____ matter.
- white
- grey
What do columns consist of?
-bundles of axons divides into spinal tracts
Sensory/Ascending Tracts
-impulses from sensory neurons/receptor UP to brain
Motor/Descending Tracts
-impulses from brain DOWN to motor neurons/effectors
What does a spinal cord injury result in?
- anethesia
- paralysis
What composes all tracts
-bundles of axons
Structure of Tracts
all axons of any tract start and finish in same structure
Function of Tracts
all axons that compose one tract serve one general function
Brain
- one of the largest organs
- 100 billion neurons (produced around birth)
- synapse are made and broken throughout life
Divisions of the Brain
- brainstem: medulla oblongata, pons, midbrain
- cerebellum
- diencephalon: hypothalamus, thalamus
- cerebrum
Brain Structure
- medulla oblongata
- pons
- midbrain (mesencephalon)
Medulla Oblongata
- lowest part
- extension of spinal cord
Pons
-connects medulla oblongata with cerebrum (cerebral cortex)
Midbrain (mesencephalon)
- near centre of brain
- cerebral penduncles conduct impulses between midbrain and cerebrum
Reticular Formation
bits of white and grey matter in the medulla
Function of Grey Matter
- autonomic reflex centres
- vital centres
- example: heartbeat, respiration, blood vessel
Sensory Tracts
-conduct impulses to higher parts of brain
Motor Tracts
-conduct impulses from higher parts of brain to spinal cord
Cerebellum
- 2nd largest part of brain
- more neurons than any other par of NS
- connected to brainstem
- cortex is grey matter
- interior is white matter
- controls muscle contractions to produce coordinated movement (balance, move smoothly, posture)
- compares motor commands of cerebrum with sensory info from muscle proprioreceptors
Diencephalon
- high traffic area
- between cerebrum and midbrain
- made of hypothalamus and thalamus
Structure of Hypothalamus
- posterior pituitary gland
- pituitary stalk
- grey matter
- one of the smallest parts
Structure of Thalamus
- dumbbell shaped
- mass of grey matter in each cerebral hemisphere
- mostely dendrites and cell bodies of neurons that have axons extending upward into sensory areas of cerebrum
Function of Thalamus
- recieves sensory info (except NOT smell)
- directs impulses to brain
- emotion
- alertness
Function of Hypothalamus
- small
- ‘heart of consiousness’
- links body and mind
- major centre for controlling the ANS (involuntary actions)
- connects nervous and endocrine systems (‘master translator’)
- hormone secretion
- appetite
- body temp
- water balance
- sleep
- wakefulness
- pleasure
- anger
- sexual arousal
- pain
Infundibulum
-stalk leading from posterior pituitary gland
Cerebrum Structure
- largest and uppermost part of brain
- oute part (cerebral cortex) has many ridges (gyri) and grooves (sulci)
- divided into hemispheres (connected by a wide, flat, bundle of nerves called corpus callosum)
What is the cerebral cortex composed of?
- 6 layers of grey matter
- mainly dendrites and cell bodies of neurons
What are the lobes of the cerebral cortex?
- frontal (motor)
- parietal (sensory)
- temporal (hearing)
- occipital (vision)
Cerebrum Function
- regulation of voluntary motor control related to posture, walking, and other repetitive movements
- mental processing (consciousness, awareness, thinking, memory, sensations, emotions)
- porture
- language (spoken and written)
Cerebral White Matter
nerve fibres arranged in bundles called tracts
Cerebral Nuclei (basal ganglia)
-islands of grey matter located deep inside the white matter of each hemisphere
Which part of the brain is commonly damaged by stroke?
-cerebrum
