Lecture 7 Nervous System

Question 1

Cell communication

Answer 1

Receptors
Visceral sensory monitor internal organs
Somatic sensory pain/touch/temp
Special - smell/taste/vision/balance/hearing

PNS
Sensory division brings info to CNS from receptors in peripheral tissues/organs

CNS
Brain and spinal chord integrate process and coordinate sensory data and motor commands
Process info

PNS
Motor division carries motor commands from CNS to peripheral tissues and systems includes:
Somatic-controls skeletal muscle
Autonomic- provides automatic regulation of smooth muscle - cardiac,glands,adipose

Effectors
SNS to Skeletal muscle
ANS to smooth/cardiac muscle, glands and adipose

Question 2

Brain size

Answer 2

Average modern human 1.4-1.6kg
Newborn human 350-500g
Elephant 6kg
Cat brain 30g

• size is not everything

Question 3

What is a Neuron

Answer 3

Excitable cells w/specialised projections which transmit information around the body by electrochemical transmission
Dendrites bring info to cell body
Axons take info away from cell body

Question 4

How do neurons communicate

Answer 4

Through an electrochemical process
Neurotransmitters releases at synapses

1 quadrillion synapses in human brain. That’s 10^15 synapses - equal to about a half billion synapses per mm3

Equivalent to 100x the whole internet

Question 5

First synapse

Answer 5

100 million years ago
Allowing decisions and applications

Question 6

Neuron structure and function

Answer 6

Dendrites - receivers and nerve impulse generators
Cell body - contains nucleus
Myelin sheath - fatty layer that insulates axon and speeds transmission
Node of Ranvier
Axon - the conducting fibre
Schwann cells - make myelin
Axon terminals- transmit into synapse

Question 7

Cell body-axon transport : kinesins

Answer 7

Axons grow outside of the cell body which houses the nucleus and other organelles such as ER. Steady transport of materials (e.g. vesicles and mitochondria) from cell body along axon length. Flow driven by kinesins (specialist motor proteins) moving along with he many microtubules in the cytoplasm within the axon

Question 8

Axon and nerve fibres

Answer 8

Nerves conduct impulses along hairlike cytoplasmic extensions called nerve fibres or axons

Axons connecting the spinal cord to the foot can be as much as 1m long and only a few micrometers in diameter

Question 9

Axons and myelin

Answer 9

Myelin sheath- expanded plasma membrane of an accessory cell - Schwann cell

Schwann cells spaced at regular intervals along the axon. Their plasma membrane wraps round the axon forming myelin sheath

Where sheath of one Schwann cell meets the next the axon is unprotected.

This region is known as the node of Ranvier and plays a role in propogation of the nerve impulse

Question 10

Integrating signals

Answer 10

A single neuron (especially in cns) may have thousands of other neurons synapsing to it. Some of these release activating (depolarising) neurotransmitter and others release inhibitory (hyperpolarising) neurotransmitters