CNS: structure and function - week 3

Question 1

what are the 3 main functions of the CNS?

Answer 1

control of internal environment

voluntary control of movement

Spinal cord reflexes

Question 2

what are the 4 divisions of the nervous system ?

Answer 2

CNS- brain + spinal cord

Peripheral NS - neurons outside the CNS

sensory division - afferent fibres transmit impulses from receptors to CNS

motor devision - efferent fibres transmit impulses from CNS to effector organs

Question 3

what are the 2 elements of the input sensory NS in functional organisation?

Answer 3

somatic sensory - consciously perceived

visceral sensory - not conscious

Question 4

what is an axon ?

Answer 4

carries electrical message(AP) away form cell body

Question 5

what are Schwann cells ?

Answer 5

form myelin sheath over length of axon

Question 6

what is a synapse ?

Answer 6

contact points between axon of one neuron and dendrite of another neuron

Question 7

the greater the__ of the axon, the greater the __ of neural transmission

Answer 7

diameter

speed

Question 8

what is a dendrite?

Answer 8

sends input from synapse to the axon

Question 9

what are the nodes of ranvier ?

Answer 9

propagation of signal/impulse along axon

Question 10

the inside of cell have a __ charge at rest (__)

Answer 10

negative

polarised

Question 11

what determines the magnitude of resting membrane potential ? (2)

Answer 11

permeability of plasma membrane to ions

difference in ion concentrations across membrane

Question 12

at rest __ channels are closed and __ channels are open.
this causes a _ membrane potential

Answer 12

sodium
potassium
negative

Question 13

how is a negative membrane potential maintained ?

Answer 13

sodium-potassium pump

Question 14

what is a sodium-potassium pump ?

Answer 14

moves 2K+ in and 3 NA+ out

uses ATP to maintain environment

Question 15

what is an action potential?(2)

Answer 15

occurs when stimulus of sufficient strength depolarises the cell

opens Na+ channels to make cell positive charge

(depolarisation)

Question 16

what is repolarisation ? (2)

Answer 16

return to resting membrane potential

K+ leaves cells rapidly
Na+ channels close

Question 17

what is the all or none law?

Answer 17

one nerve impulse initiated it travels length of neuron

(doesn’t stop)

Question 18

what is a neurotransmitter ?

Answer 18

chemical messenger released from presynaptic membrane

binds to receptors on post synaptic membrane

causes depolarisation of postsynaptic membrane

Question 19

what is excitatory postsynaptic potentials (EPSP)?

Answer 19

help achieve depolarisation

Question 20

how do EPSPs achieve depolarisation ? (2)

Answer 20

temporal summation

spatial summation

Question 21

what is temporal summation ?

Answer 21

rapid repetitive excitation from a single excitatory presynaptic neuron

Question 22

what is spatial summation ?

Answer 22

summing EPSPs from several different presynaptic neurons

Question 23

what are inhibitory post synaptic potentials (IPSP) ?(2)

Answer 23

cause hyperpolarisation (more neg resting potential)

a more neg membrane potential resist depolarisation

Question 24

what are the joint proprioceptors ? (3)

Answer 24

free nerve endings - touch/pressure

Golgi type receptors - ligaments

pacinian corpuscles - tissues around joints/skin

Question 25

what are the muscle proprioceptors/ mechanoreceptors ? (2)

Answer 25

muscle spindles Golgi tendon organs

Question 26

what is another sensory info/reflex other than muscle proprioceptors?

Answer 26

muscle chemoreceptors

Question 27

what is proprioception ?

Answer 27

the boy's sense of position based on specialised receptors that reside in the muscles, tendons and joints

Question 28

what are proprioceptors ?

Answer 28

sensors that provide info about joint angle, muscle length, and muscle tension which is integrated to give info about position of limb

Question 29

what are muscle spindles ? (3/4)

Answer 29

respond to changes in the muscle length intrafusal fibers - run parallel to normal fibres gamma motor neurons - stimulate intrafusal fibres to contract with extrafusal (muscle spindle loses so spindle reflex makes it taught again)

Question 30

what is the stretch reflex ?

Answer 30

stretch on muscle causing reflex contraction

Question 31

how does the muscle spindle work ? muscle spindles detect __ of muscle ___ neuron conduct action potentials to ____ ____ ___ neurons synapse with ___ ___ neurons stimulation of the ____ ____ neurons causes the muscle to contract and _____ being stretched

Answer 31

stretch sensory spinal cord sensory alpha motor alpha motor resist

Question 32

what does the gogli organ tendon do ? (2)

Answer 32

monitors force development in muscle - prevents damage during excessive force generation stimulation results in reflex relaxation of muscle - inhibitory neurons send inhibitory post synaptic potentials to muscle alpha motor neurons

Question 33

how does the Golgi tendon organ work ? gogli organ tendons detect ___ applied to a ___ ___ neurons conduct APs to the spinal cord ____ neurons synapse with____interneurons that synapse with ___ ___ neurons _____ of ___ ____ neuron cause muscle _____, relieving the tension applied to tendon

Answer 33

tension tendon sensory sensory inhibitory alpha motor inhibition alpha motor relaxation

Question 34

what are muscle chemoreceptors ?

Answer 34

sensitive to changes in the chemical environment surrounding a muscle

Question 35

what is a motor unit ?

Answer 35

motor neuron and all the muscle fibres it innervates

Question 36

if there's a low ratio of muscle fibres to motor neuron what does this mean?

Answer 36

allows fine motor control

Question 37

if there's a high ratio of muscle fibres to motor neurons what doe this mean ?

Answer 37

greater/gross motor control

Question 38

what happens in terms of motor unit recruitment in terms of force needed ?

Answer 38

if more force is needed , more motor units are recruited

Question 39

what is the size principle in terms of motor unit recruitment?

Answer 39

smaller motor units are recruited first during exercise

Question 40

what are the 3 types of motor units ?

Answer 40

Type S - slow type 1 fibres type FR- type 2a fast fatigue resistant type FF - type 2x fast fatigable

Question 41

what is role of cerebrum ? (3)

Answer 41

organisations of movement storage of learned experiences reception of sensory info

Question 42

what is role of cerebellum ?

Answer 42

control of movement and integration of sensory info

Question 43

what is the role of the brainstem ? (3)

Answer 43

Cardiorespiratory function locomotion muscle tone posture receive info from special senses

Question 44

what are the functions of the midbrain in the brainstem ? (1 but gave 3)

Answer 44

body movement - most important control responses to sight, eye movement and pupil dilation hearing

Question 45

what is the role of the medulla oblongata in the brain stem ?

Answer 45

coordination of body movement - important relay signals between brain and spinal cord

Question 46

what is the role of Pons in the brainstem ?

Answer 46

relay of sensory info between cerebrum and cerebellum

Question 47

what is spinal tuning ?

Answer 47

intrinsic neural networks in the spinal cord that refine voluntary movement after reviewing messages from higher brain centres

Question 48

what is the withdrawal reflex ?

Answer 48

via reflex arc contraction or muscles in response to sensory input - doesn't need higher brain centres