Communication & Homeostasis

Question 1

What’s the role of receptors in homeostasis?

Answer 1

to detect changes in stimulus involved in physiological processes.

Question 2

Why are receptors described as transducers?

Answer 2

they convert a stimulus into a nerve impulse/action potential.

Question 3

What is a Shwann cell?

Answer 3

the cell which produces the sleeve of protein and fatty material which covers some neurones.

Question 4

What is the refractory period?

Answer 4

the period of time when a neurone is unable to repeat an action potential.

Question 5

Describe how voltage-gated channels and the movement of sodium ions prevent the generation of an action potential during the refractory period.

Answer 5

The voltage-gated sodium channels are closed, preventing movement of sodium ions into the axon.
This stops the generation of an action potential.

Question 6

Give two reasons why a refractory period should follow an action potential.

Answer 6

it ensures action potentials are:
- unidirectional
- occur as discrete impulses

Question 7

‘What is the all-or-nothing’ response in terms of neurone action potentials?

Answer 7

• Neurones always generate action potentials of the same size, no matter how large the stimulus.
• The stimulus must also reach a minimum threshold or no action potential is generated.

Question 8

What is saltatory conduction?

Answer 8

the method of conduction in myelinated axons that involves action potentials jumping from one node of Ranvier to the next.

Question 9

List three factors that affect the speed of conduction along an axon.

Answer 9

• myelination
• axon diameter
• temperature

Question 10

Which neurotransmitter is found in cholinergic synapses?

Answer 10

ACh

Question 11

Name the two categories synapses can be placed in, based on how they affect the likelihood of an action potential occurring.

Answer 11

excitatory and inhibitory synapses

Question 12

What effect do inhibitory synapses have on the postsynaptic membrane?

Answer 12

hyperpolarisation

Question 13

What is summation?

Answer 13

the process in which more than one impulse is needed to generate an action potential at a synapse.

Question 14

What is temporal summation?

Answer 14

the process by which an action potential is generated from a single presynaptic neurone releasing neurotransmitters a number of times.

Question 15

What is spatial summation?

Answer 15

the process by which an action potential is generated from multiple presynaptic neurones releasing neurotransmitters.

Question 16

What is resting potential?

Answer 16

the voltage across a neurone membrane when not stimulated by an action potential.

Question 17

Describe how a resting potential is established.

Answer 17

• sodium-potassium pump.
• 3 Na+ ions are transported out of the cell, and 2 K+ ions are transported in.
• active transport.
• electrochemical gradient is established (inside of cell is more negative than the outside).

Question 18

What term is used to describe communication between adjacent cells or cells at a distance?

Answer 18

cell signalling.

Question 19

What two systems are used in animals to coordinate responses to changes in the environment?

Answer 19

• the endocrine system.
• the nervous system.

Question 20

Comment on the speed, duration and distribution of responses produced by hormones.

Answer 20

Hormones usually produce a response that is long-lasting, slow, and widespread.

Question 21

Comment on the speed, duration and distribution of responses produced by nerve impulses.

Answer 21

Nerve impulses produce responses that are usually localised, short-lived and rapid.

Question 22

What is negative feedback?

Answer 22

the type of homeostatic control in which the response to a stimulus restores a factor to its original set point.

Question 23

What is positive feedback?

Answer 23

the type of homeostatic control in which the response to a stimulus causes a factor to deviate further from its original set point.

Question 24

What is a receptor?

Answer 24

A cell or protein that detects one specific type of stimulus.

Question 25

What is an effector?

Answer 25

A part of the body, often a muscle or gland, that produces a response to a stimulus.

Question 26

What is meant by the term “ectotherm”?

Answer 26

An animal which depends on the environment to regulate its internal body temperature.

Question 27

What are (2) examples of behavioural responses ectotherms use to control their internal temperature?

Answer 27

• sun basking
• shade seeking

Question 28

What is meant by the term “endotherm”?

Answer 28

An animal that maintains a stable internal body temperature regardless of the external temperature by generating heat through metabolic processes.

Question 29

In endotherms, temperature receptors are located in which two parts of the body?

Answer 29

• the skin
• the hypothalamus

Question 30

In endotherms, which part of the brain is involved in thermoregulation?

Answer 30

the hypothalamus.

Question 31

What is seen in endotherms in response to a rise in core body temperature?

Answer 31

• vasodilation
• sweating
• relaxing hair erector muscles (to lower hair)

Question 32

What is seen in endotherms in response to a fall in core body temperature?

Answer 32

• vasoconstriction
• shivering
• contracting hair erector muscles (to raise hairs)

Question 33

Where in the body are the Islets of Langerhans found?

Answer 33

the pancreas.

Question 34

What is the function of the Islets of Langerhans?

Answer 34

to produce and secrete hormones.

Question 35

Which cells (and where) is glucagon produced in?

Answer 35

alpha cells in the Islets of Langerhans.

Question 36

Which cells (and where) produce insulin?

Answer 36

beta cells in the Islets of Langerhans.

Question 37

Define glycogenesis.

Answer 37

the conversion of glucose to glycogen.

Question 38

Define glycogenolysis.

Answer 38

the conversion of glycogen to glucose.

Question 39

Define gluconeogenesis.

Answer 39

the conversion of non-carbohydrate molecules to glucose.

Question 40

Describe how insulin binding to receptors controls the uptake of glucose into cells.

Answer 40

• insulin has a specific tertiary structure which allows it to bind to insulin receptors on the surfaces of target cells.
• binding of insulin regulates the inclusion of channel/transport proteins in the cell-surface membranes of the target cells.
• glucose enters through the channel/transport proteins.

Question 41

What type of diabetes arises when the body becomes unable to produce insulin?

Answer 41

type 1 diabetes.

Question 42

How does Type 2 diabetes arise?

Answer 42

Type 2 diabetes can arise from glycoprotein receptors being lost or being less responsive to insulin, or from insufficient insulin production in the pancreas.