Central Nervous System: Structure And Function

Question 1

Difference between sensory and motor division

Answer 1

Sensory division: afferent fibres transmit impulses from recepryors to cns

Motor division: efferent fibres transmit impulses from cns to effector organs

Question 2

Structure of a neuron:

Answer 2

1.axon-carries action potential away from cell body
2.synapse: contact point between axon of one neuron and dendrite of another neuron

Question 3

Exchange of sodium and potassium across cell membrane:

Answer 3

Maintained by sodium and potassium pump.
-Potassium tends to diffuse out of cell
-sodium and potassium pump 2k in 3 NA out

Question 4

Describe action potential

Answer 4

1.occurs when a stimulus of sufficient strength depolarises the cell

2.repolarisation-returns to resting membrane potential

3.all or non

Question 5

What is a neurotransmitter

Answer 5

Chemical messenger released from presynaptic membrane.
-binds to receptor on postsynaptic membrane
-causes depolarisation of post synaptic membrane

Question 6

What are excitatory postsynaptic potentials

Answer 6

They can promote neural depolarisation in two ways:
1.temporal summation: rapid repetitive excitation from a single excitatory presynaptic neuron
2.spatial summation: summing ESPS from several different presynaptic neurons

Question 7

What are the 3 joint proprioception

Answer 7

1.free nerve endings (touch, pressure)
2.Golgi type receptors (found in joint ligaments)
3.pacinian corpulces (tissues around joints)

Question 8

What are the 2 muscle proprioceptors

Answer 8

1.muscle spindles
2.Golgi tendon organs

Question 9

What is proprioception

Answer 9

The sense of the body’s position in spaces based on specialized receptors that reside in the muscle, tendons and joint

Question 10

What are muscle spindles

Answer 10

Respond to changes in muscle length

Question 11

What do muscle spindles consist of

Answer 11

1.Intrafusal fibres (run parallel to normal muscle fibres)

2.gamma motor neurons- stimulate intrafusal fibres to contract with extrafusal fibres

3.stretch reflex-stretch on muscle causes reflex contraction

Question 12

What is the Golgi tendon organ

Answer 12

Monitors force development in muscle, prevents muscle damage during excessive force

Stimulation results in reflex relaxation of muscle.

Question 13

What are muscle chemoreceptors

Answer 13

They are sensitive to changes in chemical environment surrounding a muscle

Inform cns about metabolic rate of muscular activity

Question 14

Structure of a motor unit:

Answer 14

Motor neurons are located in the spinal cord, and are responsible for carrying neural messages from spinal cord to skeletal muscles

Question 15

What is a motor unit

Answer 15

A motor neuron and all the fibres it innervates

Question 16

What is innervation ratio

Answer 16

Number of muscle fibres innervated by a single motor neuron.

Low ration in muscles involved in fine motor control, higher in not.

Question 17

What is the cerebellum

Answer 17

Implicated in control of movement and integration of sensory information

Question 18

What is the brainstem

Answer 18

Role in cardio respiratory function, locomotion, muscle tone, posture, receiving info from special senses

Question 19

Describe the midbrain

Answer 19

1.connects the pond and cerebral hemisphere
2.controls responses to sight, eye movement, pupil dilation, body movement and hearing

Question 20

Describe the medulla oblongata

Answer 20

Involved in autonomic function, relaying signals between the brain and spinal cord and coordination of body movements

Question 21

Describe the PONS

Answer 21

Involved in sleep and control of autonomic function.

Question 22

What is spinal tuning

Answer 22

Refers to intrinsic neural networks within the spinal cord that refine voluntary movement after receiving messages from higher brain centres

Question 23

What is the withdrawal reflex

Answer 23

Where a reflex contraction of skeletal muscles can occur in response to sensory input and is not dependant on the higher brain centres

Question 24

What 3 neurons does the spinal cord contain

Answer 24

1.motor neurons
2.sensory neurons
3.interneurons