chapter 13 p4

Question 1

The mammalian nervous system is organised structurally into two systems:

Answer 1

Central nervous system (CNS) - this consists of your brain and spinal cord.

Peripheral nervous system (PNS)

Question 2

Peripheral nervous system (PNS)

Answer 2

this consists of all the neurones that connect the CNS to the rest of the body.
These are the sensory neurones which carry nerve impulses from the receptors to the CNS, and the motor neurones which carry nerve impulses away from the CNS to the effectors.

Question 3

The nervous system is also functionally organised into two systems:

Answer 3

Somatic nervous system:

Autonomic nervous system:

Question 4

Somatic nervous system

Answer 4

this system is under conscious control - it is used when you voluntarily decide to do something.
For example, when you decide to move a muscle to move your arm.
The somatic nervous system carries impulses to the body’s muscles.

Question 5

Autonomic nervous system:

Answer 5

• this system works constantly.
• It is under subconscious control and is used when the body does something automatically without you deciding to do it - it is involuntary.
• For example, to cause the heart to beat, or to digest food.
• it carries nerve impulses to glands, smooth muscle (for example, in the walls of the intestine), and cardiac muscle.
• It is then further divided by function into the sympathetic and parasympathetic nervous system.
• Generally, if the outcome increases activity it involves the sympathetic nervous system - for example, an increase in heart rate.
• If the outcome decreases activity it involves the parasympathetic nervous system - for example, a decrease in heart or breathing rate after a period of exercise.

Question 6

sympathetic vs parasympathetic

Answer 6

Question 7

diagram The mammalian nervous system

Answer 7

Question 8

The brain is responsible for

Answer 8

processing all the information collected by receptor cells about changes in the internal and external environment.
It also receives and processes information from the hormonal system through molecules in the blood.
It must then produce a coordinated response

Question 9

The advantage of having a central control centre for the whole body is

Answer 9

that communication between the billions of neurones involved is much faster than if control centres for different functions were distributed around the body.
With the exception of reflex actions all other nervous reactions are processed by the brain.

Question 10

Gross structure of the brain

Answer 10

The brain is protected by the skull.
It is also surrounded by protective membranes (called meninges).

Question 11

five main areas of the brain:

Answer 11

• Cerebrum - controls voluntary actions, such as learning, memory, personality, and conscious thought.
• Cerebellum - controls unconscious functions such as posture, balance, and non-voluntary movement.
• Medulla oblongata - used in autonomic control, for example, it controls heart rate and breathing rate.
• Hypothalamus - regulatory centre for temperature and water balance.
• Pituitary gland - stores and releases hormones that regulate many body functions

Question 12

Gross structure of the brain diagram

Answer 12

Question 13

Different images of the brain
Many different techniques are used to study the brain in order to understand its function:

Answer 13

Question 14

Cerebrum Functions

The cerebrum receives…

Answer 14

• The cerebrum receives sensory information, interprets it with respect to that stored from previous experiences, and then sends impulses along motor neurones to effectors to produce an appropriate response.
• It is responsible for coordinating all of the body’s voluntary and involuntary responses
• The cerebrum is highly convoluted, which increases its surface area considerably and therefore its capacity for complex activity.
• It is split into left and right halves known as the cerebral hemispheres.
• Each hemisphere controls one half of the body, and has discrete areas which perform specific functions - these areas are mirrored in each hemisphere.

Question 15

Cerebral Cortex:

Answer 15

The outer layer of the cerebral hemispheres
It is 2-4mm thick.
The most sophisticated processes such as reasoning and decision-making occur in the frontal and prefrontal lobe of the cerebral cortex.

Question 16

Each sensory area within the cerebral hemispheres receives…

Answer 16

• information from receptor cells located in sense organs.
• The size of the sensory area allocated is in proportion to the relative number of receptor cells present in the body part.
• The information is then passed on to other areas of the brain, known as association areas, to be analysed and acted upon.
• Impulses come into the motor areas where motor neurones send out impulses, for example, to move skeletal muscles.
• The size of the motor area allocated is in proportion to the relative number of motor endings in it.
• The main region which controls movement is the primary motor cortex located at the back of the frontal lobe.

Question 17

Crossed Impulses and Coordination in cerebrum

Answer 17

• In the base of the brain, impulses from each side of the body cross - therefore the left hemisphere receives impulses from the right-hand side of the body, and the right hemisphere receives impulses from the left-hand side of the body.
• For example, inputs from the eye pass to the visual area in the occipital lobe.
• Impulses from the right side of the field of vision in each eye are sent to the visual cortex in the left hemisphere, whereas impulses from the left side of the field of vision are sent to the right hemisphere.
• Through the integration of these inputs the brain is able to judge distance and perspective.

Question 18

Cerebral Cortex diagram

Answer 18

Question 19

Cerebellum

Answer 19

concerned with the control of muscular movement, body posture, and balance
it does not initiate movement, but coordinates it.
Therefore, if this area of the brain is damaged, a person suffers from jerky and uncoordinated movement.
The cerebellum receives information from the organs of balance in the ears and information about the tone of muscles and tendons.
It then relays this information to the areas of the cerebral cortex that are involved in motor control.

Question 20

Medulla oblongata:

Answer 20

The medulla oblongata contains many important regulatory centres of the autonomic nervous system.
These control reflex activities such as ventilation (breathing rate) and heart rate.
It also controls activities such as swallowing, peristalsis, and coughing.

Question 21

Hypothalamus:

Answer 21

This is the main controlling region for the autonomic nervous system.
It has two centres - one for the parasympathetic and one for the sympathetic nervous system.

Question 22

the Hypothalamus has a number of functions, which include:

Answer 22

• controlling complex patterns of behaviour, such as feeding, sleeping, and aggression
• monitoring the composition of blood plasma, such as the concentration of water and blood glucose - therefore it has a very rich blood supply
• producing hormones - it is an endocrine gland, that is, it produces hormones.

Question 23

Pituitary gland:

Answer 23

This is found at the base of the hypothalamus.
It is approximately the size of a pea but it controls most of the glands in the body.
It is divided into two sections:

Question 24

two sections of pituitary gland

Answer 24

• Anterior pituitary (front section) - produces six hormones including follide-stimulating hormone (FSH), which is involved in reproduction and growth hormones.
• Posterior pituitary (back section) - stores and releases hormones produced by the hypothalamus, such as ADH involved in urine production.

Question 25

Pituitary gland diagram

Answer 25

Question 26

What is a reflex action

Answer 26

When the body is in danger, it can respond to situations without conscious thought.
This causes a faster response, preventing or minimising damage to the body.

Question 27

What is a reflex:

Answer 27

an involuntary response to a sensory stimulus.

Question 28

What is the reflex arc:

Answer 28

The pathway of neurones involved in a reflex action
Most reflexes follow the same steps between the stimulus and the response:
* Receptor - detects stimulus and creates an action potential in the sensory neurone.

• Sensory neurone - carries impulse to spinal cord.
• Relay neurone - connects the sensory neurone to the motor neurone within the spinal cord or brain.
• Motor neurone - carries impulse to the effector to carry out the appropriate response.

Question 29

An example of a reflex arc:

Answer 29

when you touch a hot candle - this is known as a withdrawal reflex.
Before your brain registers that your hand is hot, the muscles in your arm have already pulled your hand away from the danger, minimising damage to your hand.

Question 30

An example of a reflex arc diagram

Answer 30

Question 31

What is the spinal cord:

Answer 31

a column of nervous tissues running up the back.
It is surrounded by the spine for protection.
At intervals along the spinal cord pairs of neurones emerge.

Question 32

spinal cord diagram

Answer 32