Approaches- biopsychology- The Peripheral nervous system

Question 1

How many spinal nerves is the PNS made up of?

Answer 1

31.

Question 2

What are two types of cells in the CNS?

Answer 2

Sensory nervous cells- to CNS

These cells carry information from internal organs or from external stimuli.

Motor nervous cells- from CNS

These cells carry information from the CNS to organs, muscles and glands.
The motor nervous system is divided into the somatic nervous system and the autonomic nervous system.

These cells carry information to and from the central nervous system.

Question 3

The motor nervous system is divided into what two systems and what do these systems do?

Answer 3

The somatic nervous system.
Controls skeletal muscle as well as external sensory organs such as the skin. This system is said to be voluntary because the responses can be controlled consciously. Reflex reactions of skeletal muscle however are an exception. These are involuntary reactions to external stimuli.

The autonomic nervous system.
Controls involuntary muscles. such as smooth muscle and cardiac muscle and is vital for maintaining homeostasis as it helps the organism become independent of their environment (e.g. can control our body temp, regardless of the weather). This system is also called the involuntary nervous system. The autonomic nervous system can further be divided into the parasympathetic and sympathetic divisions.

Question 4

What does the parasympathetic division control?

Answer 4

Various functions which include inhibiting heart rate, constricting pupils, and contracting the bladder.

Question 5

What does the sympathetic division often do?

Answer 5

The opposite to the parasympathetic.
It usually has the opposite effect when they are located within the same organ.
Nerves of the sympathetic division speed up heart rate, dilate pupils, and relax the bladder.
The sympathetic system is also involved in the flight or fight response. This is a response to potential danger that results in accelerated heart rate and an increase in metabolic rate.

Question 6

Are the two branches parasympathetic and sympathetic usually in balance with each other?

Answer 6

Yes, but they shift in favour of one when the body’s physiological requirements need it. E.g. If threatened/ danger, the hypothalamus will register the threat and activate the sympathetic branch so we can fight or flight (through added energy gained through adrenaline release).

Question 7

How do neurones carry information?

Answer 7

As tiny electrical signals called action potentials.

Action potentials can be conducted along the neuron at a rate of up to 400 impulses per second.

Question 8

What are three types of neurones?

Answer 8

Sensory neurones
Relay/inter neurones
Motor neurones

Question 9

What do sensory neurones do?

Answer 9

Tell the rest of the brain about the internal and external environment by processing information through the 5 senses and pain.
Sensory information is carried in sensory (or “afferent”) pathways which run from sensory receptors through spinal nerves to the spinal cord and onwards to the brain (although visual and auditory information remains within the brain). Unipolar neurons (only transmit messages).
Example;
burning your hand
or stubbing your toe.

Question 10

What do relay/inter neurones do?

Answer 10

Carry messages from one part of the CNS to another. They connect motor and sensory neurons. Multipolar neurones (transmit and receive messages). The majority of neurones in the brain are relay neurones.

Question 11

What do motor neurones do?

Answer 11

Carry signals from the CNS to organs, glands and muscles (effectors) via “efferent” pathways. Multipolar neurones (transmit and receive messages).

Question 12

What is the reflex arc?

Answer 12

A reflex arc is the nerve pathway which makes such a fast, automatic response possible.
It does not matter how brainy you are- you will always pull your hand away from a flame without thinking about it. It is in-built/innate behaviour and we all behave in the same way.

Question 13

What happens when an organism demands a very quick response?

Answer 13

Reflex reactions in humans are controlled by the reflex arc.
When the safety of an organism demands a very quick response, the signals may be passed directly from the sensory neuron via a relay neuron (which sends the signal to the brain to acknowledge the action), to a motor neurone for instant, unthinking actions. This is the reflex action.
It is not a thought processing action.

Question 14

What is the flowchart for the reflex action?

Answer 14

Stimulus –> pain receptor stimulated –>
signal sent along sensory neuron –> signal sent along relay neuron (and message sent to brain) –> signal sent along motor neuron –> effector muscle contracts (response) reflex.

Question 15

What is saltatory conduction?

Answer 15

In advanced animals such as mammals, many neurones making up the nervous system are covered in fatty myelin sheath. There are gaps in the sheath called nodes of Ranvier, where the neutral cell membrane is exposed.
Action potentials can jump faster from gap to gap to dramatically increase the speed impulses can travel.
This faster transmission enables faster information processing and therefore development of complex cognitive abilities.
This method of neural transmission is called salutatory conduction.

Question 16

What is the process of synaptic transmission?

Answer 16

Where two neurones meet, there is a tiny gap using chemicals released by a neurone. The chemical diffuses across the gap makes the next neurone transmit an electrical signal.

1) An electrical impulse travels along an axon to the terminal.
2) This triggers the nerve-ending of a neuron to release chemical messengers from synaptic vesicles called neurotransmitters.
3) These chemicals diffuse across the synapse (the gap made of synaptic fluid) and bind with receptor molecules on the membrane of the receiving neuron cell body/dendrite.
4) The receptor molecules on the second neuron bind only to the specific chemicals released from the first neuron. This stimulates the second neuron to transmit the electrical impulse.

Question 17

What is synaptic transmission?

Answer 17

“The process by which nerve impulses are carried across the small gap, the synapse, between one neuron and another. The nerve impulse is an electrical signal which is carried by chemicals called neurotransmitters”.
This occurs at high speed, i.e. when processing visual information, most seems to be encoded in the first 50-100 milliseconds of neuronal activity.

Question 18

Who is the researcher that provided evidence about synaptic transmission?

Answer 18

Yamamoto (2001) explained why they touched in two places simultaneously we night perceive the sensation at different times. Since there is a difference in the distance he messages may have to travel, one reaches the brain at a different time to the other.

Question 19

Only certain neurotransmitters can unlock a message channel true or false?

Answer 19

True.
Not all messages prompt activation in the same way. It depends on the “action potential” of the post-synaptic neuron and the message type received.

Only certain neurotransmitters can “unlock” a message channel in certain receptors in the post-synaptic neurone (like a lock and key system).

When the right key (neurotransmitter) meets the right lock (receptor) a specific ion channel in the membrane is opened up, a bit like a door.

Ions then flow through the membrane into the neuron along their specific pathways. This flooding of ions can cause a “potential” in the dendrites. These potentials can be excitatory or inhibitory.

Question 20

Why do excitatory potentials make it more likely for an action potential to generate a presynaptic neuron?

Answer 20

Make it more likely for an action potential to generate in a presynaptic neuron, which increases the probability of an action potential occurring in a postsynaptic cell because positively charged ions flood into the receiving cell (like the accelerator in a car).

Question 21

What are examples of excitatory neurotransmitter actions?

Answer 21

Glutamate is used at the great majority of fast excitatory synapses in the brain and spinal cord.

Dopamine regulates motor behaviour. It plays a critical role in the reward system; people with Parkinson’s disease have been linked to low levels of dopamine and people with schizophrenia have been linked to high levels of dopamine.

Serotonin is monoamine neurotransmitter. It functions to regulate appetite, sleep, memory and learning. It is speculated to have a role in depression, as some depressed patients are seen to have lower concentration of metabolites of serotonin in their cerebrospinal fluid and brain tissue.

Adrenaline is released from the adrenal glands. It plays a role in sleep, with one’s ability to stay/ become alert, and the flight-or flight response.

Question 22

What are inhibitory potentials?

Answer 22

Make it less likely to fire as negatively charged ions flood into the receiving cell. If the message is likely to be stopped at the post synaptic neuron, it is called an inhibitory synapse.

Question 23

What are examples of inhibitory neurotransmitter actions?

Answer 23

GABA is an inhibitory neurotransmitter as it’s binding on the post synaptic receptor enables negatively charged chloride ions to enter the receiving cell through the receptor channel.
Drugs to reduce anxiety (benzodiazepines) can be prescribed to prevent excitation (therefore anxiety) by enhancing the effectiveness of GABA and by reducing the effect of excitatory pathways such as serotonin.

Question 24

How do all of these different signals affect the overall activity in the neuron?

Answer 24

Excitatory and inhibitory messages compete with each other at numerous synapses of a neuron; this determines whether or not the action potential at the presynaptic will regenerate at the postsynaptic membrane. Action potentials will fire if the membrane is depolarised (caused by increase in positive charge to the membrane).

Excitatory transmitters (or EPSPs) increase the likelihood of a postsynaptic action potential occurring and therefore excite the nervous system.

Inhibitory transmitters (or IPSPs) decrease this likelihood and therefore inhibits/calm the nervous system. (calming).