The Neevous System

Question 1

Give functions of the nervous system;

Answer 1

Allows to sense the environment and respond through muscle movements

Allows us to process complex information to make decisions

Can store information (memory)

Mediates emotion

Question 2

What is the job of the central nervous system?

Answer 2

Processes information and includes the brain and spinal cord

Question 3

What is the job of the peripheral nervous system?

Answer 3

Contains the inputs (sensory) and outputs (motor) to the CNS

Question 4

What are neurons (nerve cells) and where are they found?

Answer 4

Electrically excitable cells with the ability to transmit a nerve impulse

Found in all multicellular animals from jellyfish to man

Question 5

What is the soma?

Answer 5

Cell body containing nucleus

Question 6

What are the dendrites of the neuron?

Answer 6

Receives inputs and transmit impulses towards cell body

Question 7

What is the axon?

Answer 7

Transmits output away from cell body

Question 8

What are axon terminals?

Answer 8

Transmits outputs by forming synapses (connections) to other neurons or muscle cells

Question 9

Describe the 3 types of neuron;

Answer 9

Sensory- receives sensory information from periphery & transmits this info to interneurons in the central nervous system

Motor- receives information from internruons within central nervous system and transmits this to muscle

Interneurons- present within the brain/spinal cord and serve to connect sensory and motoneurons inter neural circuits

Question 10

The somatosensory system consists of;

Answer 10

Mechanoreceptors - detect touch

Nociceptors - detect pain & heat

Proprioceptors - detect muscle tension

Question 11

Where are somatosensory neurons located?

Answer 11

In ganglia (clusters of neurons)

Which lie alongside the brain & spinal cord

Question 12

Where are somatosensory neurons in the head located?

Answer 12

Within cranial ganglia outside of the brain

Question 13

Describe the structure of the retina;

Answer 13

Rods and cones are specialised photoreceptor cells

Retina has a complex 6-layered structure= allows processing of sensory info

Retinal ganglion cells transmit information to the brain

Question 14

Describe motor neurons;

Answer 14

Control muscle contraction

Soma of them are located within the spinal cord

Release neurotransmitter which leads to electrical impulses within the muscle leading to contraction

Question 15

Where are interneurons located and what is their function?

Answer 15

Located- within the central nervous system

Serve to link sensory inputs to motor outputs

Can form Complex regulatory pathways

Question 16

What is the point of the knee-jerk flex?

Answer 16

Stretches the muscle spindle in the quadriceps muscle

Nerve endings detect stretch and transmit the info along their axons to the spinal cord

Question 17

What are glia and their functions?

Answer 17

Non-neuronal cells located within the central & peripheral nervous systems

Functions- provide electrical insulation
- maintain homeostasis

Also required for rapid transmission of electrical impulses

Question 18

What do you know about Schwann cells?

Answer 18

Wrap around the axons of sensory & motoneurons

Contain myelin which acts as an electrical insulator

Question 19

What are astrocytes?

Answer 19

Found in the central nervous system

Star cell

Question 20

What are oligodendrocytes?

Answer 20

Found in the CNS

Wrap around the axons providing a myelin sheath

Question 21

What are ependymal cells?

Answer 21

Ciliated cells which line surface of ventricles of the brain and the central canal of the spinal cord

Secrete cerebrospinal fluid which serves to cushion brain and also provides nutrients

Question 22

Describe the grey matter and white matter of the brain?

Answer 22

Grey matter -> where cell bodies of the neurons occur

White matter -> where axons are located and synapses are made
White due to high fat content

Question 23

Describe the V=IR in ohms law;

Answer 23

Voltage- or potential difference is the force that drives the movement of ions

Current (I) - measure of the rate of flow of ions

Resistance - is a measure of the opposition to movement of ions

Question 24

Describe the membrane as a barrier;

Answer 24

Plasma membrane separates the cytoplasm from tissue fluid

Means conc of an ion may be different inside the cell to outside

Question 25

Describe the ions unevenly distributed across membrane;

Answer 25

Resting membrane potent ion results from the unequal distribution of ions across the membrane

Potassium- higher concentration inside the cell

Sodium&chlorine- are higher outside the cell

Question 26

Movement of ions across the membrane are determined by what 3 factors;

Answer 26

1 conc gradient of the ion
• ions love from high to low

2 electrical gradient (voltage)
• opposites attract - positives draw towards negatives

3 selective permeability of membrane
• some ions can pass freely across membrane, others are impeded

Question 27

Ion channels can be gated by;

Answer 27

Membrane potential

Ligand binding

Mechanical stimuli

Question 28

What is the resting potential?

Answer 28

The cell normally has a negative change relative to the extracellular fluid

(-70mV)

Question 29

What happens during depolarisation?

Answer 29

Voltage-gated sodium channels open

Na+ enters cell

Membrane potential increases

Question 30

What happens during repolarisation?

Answer 30

Voltage-gated potassium channels open

K+ leaves cell

Membrane potential decreases

Question 31

What happens once the action potential has been triggered?

Answer 31

The membrane will rapidly depolarise

Voltage-gated NA+ channels have theshold at which they will open

Action potential is porpargated along length of axon

Question 32

Synaptic inputs to the neuron result in small changed in membrane potential this can be either;

Answer 32

EPSPs- excitatory post-synaptic potentials = depolarise membrane

IPSPs- inhibitory post-synaptic potentials = hyperpolarise membrane

Question 33

Describe the synapse;

Answer 33

A junction between neurons across which nerve impulses are propagated

Two types of synapse;
- chemical synapse
- electrical synapse (gap junction)

Question 34

What happens at a chemical synapse the prrsynaptic neuron releases a neurotransmitter…

Answer 34

Diffused across the synaptic cleft and binds to a receptor on the postsynaptic neuron

Question 35

What results from the binding of the neurotransmitter to its receptor?

Answer 35

Opening of ligand-gated Jon channels resulting in either an EPSP or IPSP