Case 1 - intro to the nervous system

Question 1

what is perception

Answer 1

constructive process in the brain that depends upon both information about stimuli (sensations) and the mental structure of the perceiver.

Question 2

what is pain derived from

Answer 2

is a perception derived from sensory input between nociceptors

Question 3

what is nociception

Answer 3

is the sensory nervous systems process of encoding noxious stimuli. it deals with a series of events and processes required for an organism to receive a painful stimulus, convert it to a molecular signal, and recognise and characterise the signal in order to trigger an appropriate defence response

Question 4

what are neurones

Answer 4

cells which integrate information and pass it on

Question 5

what are glia

Answer 5

‘support cells’, maintaining the environment and ‘moping up’

Question 6

how much of the cardiac output is directed to the brain

Answer 6

25-30% of cardiac output is directed to the brain

Question 7

what two substances from blood can the brain only use

Answer 7

glucose and O2

Question 8

what is there no build up of in the brain

Answer 8

lactate buildup from anaerobic metabolism

Question 9

what is excitotoxicity

Answer 9

over exposure to glutamate with actions on NMDA receptors which allow Ca influx and can cause swelling and rupture

Question 10

morphological features of a neurone

Answer 10

Question 11

what are the three types of synaptic connection

Answer 11

• axodendritic
• axosomatic
• axoaxonic

Question 12

diagram explaining the simple circuits of synapse connection

Answer 12

Question 13

what do dendrites do

Answer 13

they ‘collect’ information from synaptic outputs, potentially from relatively long distances away, with the membrane at the soma summing all of the dendritic EPSPs and IPSPs both across time and location

Question 14

what is an EPSP

Answer 14

excitatory postsynaptic potential

Question 15

what is an IPSP

Answer 15

Inhibitory postsynaptic potential

Question 16

what happens if the membrane depolarisation at the exon hillock reaches threshold

Answer 16

an action potential is initiated, which travels down the axon to the axon terminal which releases a neurotransmitter

Question 17

what is the neurone used in this

Answer 17

an analoge-to-digital converter (D2A etc)

Question 18

what does continuously varying changes in the cell soma membrane potential do

Answer 18

gives rise to discrete ‘all or none’ action potential events

Question 19

how many synapses can there be onto any single Nerone

Answer 19

can be hundreds to thousands

Question 20

what are the 4 reflex types

Answer 20

• stretch reflex
• inhibitory reflex
• flexor reflex
• crossed extensor reflex

Question 21

what do ligaments bind

Answer 21

ligaments bind bone to bone

Question 22

what do tendons bind

Answer 22

tendons bind muscle to bone

Question 23

what is flexion

Answer 23

the closing of a joint e.g contraction of the biceps (flexor muscle) - cases the joint at the elbow

Question 24

what extension

Answer 24

the opening of a joint e.g contraction of the triceps (an extensor muscle) opens the joint at the elbow

Question 25

what would contraction of both extensor and flexor cause

Answer 25

results in stiffness at the joint with no movement

Question 26

what has to happen in order to get movement

Answer 26

the antagonist muscle must relax during agonist contraction - this is an important concept to understand

Question 27

what happens during flexion of the elbow joint

Answer 27

- the biceps are the agonist - the triceps are the antagonist

Question 28

what happens during extension of the elbow Joint

Answer 28

- the triceps are the agonist - the biceps are the antagonist

Question 29

what is a reflex

Answer 29

uses existing neural circuits In the spinal cord - reflexes do not require learning

Question 30

the sensor, integrator and effect model

Answer 30

Question 31

stretch reflex

Answer 31

taping the tendon connecting a muscle to a bone causes that muscle to stretch slightly. this stretch is deterred by a sensor which through a reflex circuit causes the muscle to contract

Question 32

why does the muscle contract

Answer 32

to counteract the imposed stretch

Question 33

describe the 'knee jerk' reflex

Answer 33

stretch of the patellar tendons stretches the quadriceps. the induces reflex quadriceps contraction. as the quadriceps is an extensor muscle, contraction 'opens' the knee joint and straightens the leg

Question 34

what does the knee jerk reflex protect from

Answer 34

protects the muscle from damage due to over-stretching.

Question 35

what is this reflex also called

Answer 35

the myotatic reflex

Question 36

what are the two main types of muscle fibres

Answer 36

- extrafusal: main body of the muscle - intrafusual: lie within the extrafusal and forms the muscle spindle

Question 37

diagram of knee jerk reflex

Answer 37

Question 38

what is the spindle response

Answer 38

a mechanoreceptor

Question 39

relationship between the main muscle fibres and the spindles

Answer 39

parallel

Question 40

what happens when muscle fibres stretch

Answer 40

the spindle also stretches increasing the sensory signal in its Group 1a afferents. these project to the spinal cord via the dorsal horn

Question 41

diagram showing spindle strech

Answer 41

Question 42

what happens when muscle fibres contract

Answer 42

the muscle length shortens, making the spindle fibres go slack, loose and stop signalling stretch

Question 43

what counteracts this

Answer 43

the gamma motor neurone excites the spindles intrafusal fibres to maintain spindle muscle tone during contraction

Question 44

spindle being slack explanation and compensation

Answer 44

when the spindle is slack, there is not information about muscle length being transmitted to the spinal cord. this is bad as the position of the joint and related muscle state of contraction are vital in order to effect controlled movement. contracting the intrafusal fibres compensates for this state by restoring spindle output. in such a case the brain can calibrate the 'new' value of spindle output against the amount of activity in the gamma motor neurones to estimate true length of the main muscle

Question 45

what produces muscle contraction

Answer 45

motor units are small in order to deliver fine control of movement. motor units air large for muscles involved in large powerful movements where u need a small range of simple powerful movements

Question 46

diagram of muscle contraction

Answer 46

Question 47

arrangement of motor neurones in the spinal cord diagram

Answer 47

Question 48

what are the steps underlying monosynaptic stretch reflex

Answer 48

1. stretching of muscle stimulates muscle spindles 2. activation of sensory neurone 3. information processing at motor neurone 4. activation of motor neurone 5. contraction of the muscle

Question 49

how is the flexor muscle inhibited

Answer 49

via synapse at 2 and inhibitory interneurone

Question 50

what can abnormal oscillation of flexion and extension around the joint be often seen in

Answer 50

spasticity

Question 51

how does the Golgi tendon organ lie in relation to tendons and muscles

Answer 51

it lies in series with muscle fibres (spindles are parallel)

Question 52

what does Golgi tendon organ do

Answer 52

responds to tension developed by muscle during isometric contraction. prevents heavy loading of muscle causing damage.

Question 53

ow does the Golgi tendon organ work

Answer 53

works by activating inhibitory interneurones to relax the muscle immediately

Question 54

diagram showing lay out of Golgi tendon organ and spindle

Answer 54

Question 55

what is the inverse of a stretch reflex

Answer 55

when the agonist muscle is excited and aids in extension of the joint. at the same time the antagonist muscle is relaxed, so therefore inverse of a stretch reflex

Question 56

diagram of the flexor reflex

Answer 56

Question 57

what is the crossed extensor reflex

Answer 57

flexors in the withdrawing limb contract and the extensors reflex, while in the other limb the opposite happens. signals travelling via the spinal cord contract the contralateral muscles of the hips and abdomen. this shifts the body centre f gravity over the extended leg

Question 58

summary: please please work.

Answer 58

Neurones combine to form simple and highly complex circuits. simplest neuronal circuit organisation can be seen in the 4 reflex types.