Nervous System

Question 1

what are 2 main divisions of the nervous system

Answer 1

• central nervous system (CNS)
• peripheral nervous system (PNS)

Question 2

Somatic nervous system
autonomic nervous system
central nervous system
peripheral nervous system

Answer 2

• the voluntary nervous system
• involuntary nervous system
  -consists of the brain and spinal cord
• includes the sensory & motor neurons that connect the CNS to the rest of the body.

Question 3

The divisions of the autonomic nervous system (ANS)

Answer 3

the sympathetic & parasympathetic

The parasympathetic nervous system calms the body, conserving its energy, sleep, relaxing, acetylcholine is released & acts on SAN to decrease heart rate

The sympathetic nervous system – fight or flight. Increasing its energy in stressful situation: using noradrenaline neurotransmitters. Acts in SAN to accelerate heart rate.

Question 4

neurone structure

Answer 4

Axon- a long nerve fibre of a neurone which carries a nerve impulse

Dendrites- extensions from the cell body which connect with neighbouring neurones

Schwann cell- specialised cell associated the axons of with myelinated neurones, forms the insulating myelin sheath.

Myelin sheath- fatty insulating layer around some axons produced by the Schwann cell

Nodes of Ranvier- gaps between the Schwann cells that enable saltatory conduction

Motor neurone- sends impulses from the spinal cord/CNS to the effector (muscle of gland).

Sensory neurone – sends impulses from a sensory receptor to a relay neurone in the spinal cord/CNS

Relay neurone- carry messages from one part of the CNS to another.

Question 5

Reflex Arc

Answer 5

Receptor – a specialised cell that responds to changes in the surrounding environment

Effector - muscle or glands

Action potential – a change in electrical potential along the membrane of a nerve or muscle cell. (Nerve impulse)

Glial cell – cells that provide support for neurons

Reflex arc - stimulus, receptor, sensory neuron, relay neuron, motor neuron and effector that are involved in a quick response to a trigger an action potential

Question 6

Action potential

Answer 6

is the neural impulse; a brief electrical charge that travels down an axon.

Question 7

sodium-potassium pump
resting potential
depolarisation
repolarisation
hyperpolarisation

Answer 7

• a carrier proteins that uses ATP to actively transport 3Na+ sodium ions out of a cell and 2K+ potassium ions into the cell.
• is the state of the neuron when not firing a neural impulse, the neurone is polarised and negative inside . -70mV
• when stimulated, voltage gated sodium ion channels open and more sodium ions diffuse into the neurone. The inside of the membranes becomes positive +35mV
  -Sodium channels close and potassium voltage gated channels become activated and open, causing K+ to diffuse out of the cell for the membrane to repolarise
• Potassium ion channels are slow to close so there is a slight overshoot where too many potassium ions out of the neurone, so the potential difference is more negative than the resting potential.

Question 8

what is refractory period, myelinated axons and saltatory conduction?

Answer 8

• the time following an action potential during which a new action potential cannot be initiated
• axons covered with myelin sheaths, with gaps between them ( nodes of Ranvier), transmission is much faster.
• rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.

Question 9

synapses

Answer 9

• Presynaptic neuron conducts impulses toward the pre-synaptic knob
• Synaptic vesicles is membrane-bounded compartment where the neurotransmitter is kept
• neurotransmitters are chemical messengers that cross the synaptic cleft
  Mitochondrion- an organelle found in large numbers in the pre-synaptic neuron which synthesise neurotransmitters
  synaptic cleft- tiny gap that separates the axon terminal of one neuron from the dendrite terminal of the next neuron.
  how neurotransmitters work- they are released then diffuse across the synaptic cleft. They bind to receptors in the past synaptic neurone if enough neurotransmitters bind, an action potential will, be generated in the post-synaptic neurone

Question 10

synaptic transmission steps

Answer 10

1. Depolarisation of presynaptic membrane
   2 calcium channels open & calcium ions enter synaptic knob
2. calcium ions cause synaptic vesicles to fuse with presynaptic membrane & release acetylcholine/neurotransmitter
3. Acetylcholine/neurotransmitter diffuses across synaptic cleft
4. Acetylcholine attaches to receptors on the postsynaptic membrane
5. Sodium ions enter postsynaptic neurone leading to depolarisation

Question 11

neurotransmitters & dugs at synapses

Answer 11

• Parkinson’s disease is disorder of the CNS that affects movement due to lack of dopamine, often including tremors
• Serotonin is a neurotransmitter that affects hunger, sleep,
  arousal and mood. Lack of serotonin can cause depression
  -Drugs & the synapse:
  1. stimulate or inhibit neurotransmitter release
  2. stimulate or block postsynaptic receptor molecules
  3. Inhibit reuptake