The Human Nervous System - Part 2 (T2)

Question 1

What is a reflex and what is its purpose?

Answer 1

A reflex is an involuntary action, meaning we have no control over it. This has evolved to help an organ survive, for example you don’t think about pulling your hand away from a flame, you just do it.

Question 2

Give two examples of nervous communication and how they work..

Answer 2

1) pulling your hand away from a hot flame:

• receptor detects a stimulus (heat)
• pain receptor is stimulated
• the signal is sent along a sensory neuron
• the signal is passed along the relay neuron (sent to the brain)
• the signal is sent along the motor neuron
• effector muscle contracts, pulling the hand away

2) your pupil adjusting to bright or dim light:

In bright light…

• radial muscles of the iris relax
• circular muscles of the iris contract
• less light enters the eye through the contracted pupil

In dim light…

• radial muscles of the iris contract
• circular muscles of the iris relax
• more light enters the eye through the dilated pupil

Question 3

In four steps break down what happens during a reflex action…

Answer 3

• the stimulus is detected by a receptor cell
• sensory neurone sends signal to relay neurone
• motor neurone sends signal to effector
• effector produces a response

Question 4

What other names does the relay neurone go by?

Answer 4

• the interneurone
• the association neurone
• the internuncial neurone

Question 5

What is the reflex arc?

Answer 5

The process of impulses being passed between pathways in a simple reflex:

Receptor - sensory neurone - CNS - motor neurone - effector

Question 6

In a reflex knee-jerk, what is the receptor and what is the effector?

Answer 6

The receptor is a receptor in the leg extensor muscle and the effector is the leg muscle itself.

Question 7

Actions which are taken by the body to react to stimuli are called..

Answer 7

Responses

Question 8

The body detects a stimulus using specialised cells in the body called..

Answer 8

Receptors

Question 9

The body responds to stimuli using..

Answer 9

Effectors

Question 10

Which two organ systems in the body are continuously working to detect and respond to stimuli?

Answer 10

• the nervous system

- the endocrine system

Question 11

What is thermoregulation?

Answer 11

Thermoregulation is the body’s maintenance of a constant temperature.

Question 12

What is the main organ involved in maintaining a constant body temperature?

Answer 12

The skin.

Question 13

What are the two main layers that make up the human skin called?

Answer 13

• the epidermis

- the dermis

Question 14

What is the function of the epidermis and dermis in human skin?

Answer 14

The primary function of the epidermis is to protect the dermis which contains most of the structures, and also to protect the body from ultra-violet rays.

Question 15

What is the external surface of the epidermis made of?

Answer 15

Dead cells.

Question 16

What main structures does the dermis contain?

Answer 16

• hair, sweat and sebaceous glands
• sense receptors
• erector muscles
• blood vessels

Question 17

In the human skin dermis, what do the erector muscles do?

Answer 17

They are involved in the control of body temperature.

Question 18

Name some ways in every day life that a normal healthy body gains and loses heat…

Answer 18

Metabolic reactions of the body such as respiration produce heat energy. This production of heat energy is further exacerbated by muscle activity which further increases the production of heat.

The body gains heat from the sun.

The body gains heat from eating hot food.

Heat is lost or escapes from the body by conduction through exposed skin.

Sweat or water on the skin will absorb heat from the body which will evaporate, reducing body temperature.

Question 19

When our body’s temperature rises and we overheat, the body responds in several ways to lose heat and return the temperature back to the norm. Describe four of these processes…

Answer 19

1) vasodilation: blood vessels near the surface of the skin widen, increasing the blood flow and bringing the blood closer to the surface of the skin thus causing the body to lose heat quickly.
2) sweating: the sweat glands secrete sweat onto the surface of the skin through the sweat pores. The sweat absorbs body heat which is lost through evaporation.
3) hairs lie flat: the hair erector muscles relax making the hairs lie flat on the skin surface. When the hairs are flat, less air is trapped between them and so more heat is lost.
4) body’s metabolic reactions slow down: the reactions in the body slow down to produce less heat.

Question 20

What the body temperature falls, describe four processes that the body responds with to bring the temperature back up to the norm…

Answer 20

1) vasoconstriction: blood vessels near the surface of the skin get narrower, taking the blood away from the surface of the skin, deeper into the body, causing the body to lose less heat.
2) shivering: the muscles of the body start to contract and begin to produce more heat through respiration.
3) hairs stand up: the hair erector muscles contract making the hairs stand up on the skin surface. When the hairs are standing air is trapped between them forming a layer of insulation and so less heat is lost.
4) body’s metabolic reactions speed up: the reactions within the body speed up to produce more heat.