Bio 4: Communication and homeostasis Flashcards Preview

Biology A2 > Bio 4: Communication and homeostasis > Flashcards

Flashcards in Bio 4: Communication and homeostasis Deck (65):
1

Stimulus

Any change in the environment that causes a response

2

Response

A change in behaviour or physiology as a result of a change in the environment

3

Good communication system

-Cover the whole body
-Enable specific communication
-Rapid communication
-Short term and long term

4

Homeostasis

maintenance of the internal environment in a constant state despite external changes

5

Negative feedback

Process that brings about a reversal of any change in conditions. Ensures the optimum steady state can be maintained, as the internal environment is returned to the original set of conditions after any change.

6

Positive feedback

Process that increases any change detected by the receptors. Tends to be harmful.

7

Ectotherm

Organism that relies on external sources of heat to regulate its body temperature

8

Endotherms

Organism that can use internal sources of heat, such as heat generated from metabolism in the liver, to maintain it's body temperature

9

Sweat Glands (response to high temp)

Secrete more sweat onto skin, water in sweat evaporates, using heat from blood to supply latent heat of vaporisation

10

Hairs on skin (response to high temp)

Hairs lie flat, providing little insulation, thus more heat lost by convection and radiation

11

Arterioles leading to capillaries in skin (response to high temp)

Vasodilation allows more blood into capillaries near the skin surface; more heat can be radiated from the skin surface

12

Liver cells (response to high temp)

Rate of metabolism is reduced; less heat generated from exergonic reactions such as respiration

13

Skeletal muscles (response to high temp)

No spontaneous contractions

14

Thermoregulatory centre

In the hypothalamus, monitors blood temperature and any changes in core body temperature

15

Cones and rods

In the eye retina, detect changes in light intensity and wavelengtyh

16

Olfactory cells

In the nose, detect the presence of volatile chemicals

17

Taste buds

Detect the presence of soluble chemicals

18

Pacinian corpuscles

Detect pressure on skin

19

Sound receptors

Cochlea, detect vibrations in air

20

Proprioceptors

Detect length of muscle fibres

21

Transducers

Convert one energy form to another

22

Polarised membrane

A membrane with a potential difference across it. This is the resting potential

23

Depolarisation

The loss of polarisation across the membrane. The period when sodium ions entering the cell are making the inside less negative with respect to the outside.

24

Generator potential

Small depolarisation caused by sodium ions entering the cell

25

Action potential

Achieved when the membrane is depolarised to a value of about +40mV. The membrane depolarises and reaches a threshold level, sodiums enter and action potential is reached.

26

Motor neurones

-Action potential from the CNS to an effector
-Cell body in the CNS
-Long axon
-Numerous dendrites

27

Sensory neurones

-Action potential from sensory receptor to CNS
-Long dendron
-Cell body outside of the CNS
-Short axon
-Numerous dendrites

28

Resting potential

Potential difference across the cell membrane while at rest. This is about -60mV inside the cell compared with the outside.

29

Voltage-gated channels

Channels in the cell membrane that allow passage of charged particles or ions. The gate opens and closes, when there is a change in potential difference across the membrane.

30

Threshold potential

Potential difference of roughly -50mV, the depolarisation has to reach this value for an action potential to be generated

31

Refractory period

The short period of time after firing during which it is more difficult to stimulate a neurone. Ensures that action potentials are only transmitted in one direction.

32

Hyperpolarised

When the membrane is more highly polarised than the usual resting state. (More negative than -60mV)

33

Local currents

Movement of ions along the neurone. The flow of ions is caused by an increase in concentration at one point, which causes diffusion away from the region of higher concentration.

34

Myelin sheath

Insulating layer of fatty matieral, Sodium and potassium cannot diffuse through. Increases the speed of conduction.

35

Saltatory conduction

Refers to the 'jumping conduction', where the action potential appears to jump from one node of ranvier to the next.

36

Neurotransmitter

A chemical that diffuses across the cleft of the synapse to transmit a signal to the postsynaptic neurone

37

Cholinergic synapse

Those that use acetylcholine as their transmitter substance

38

Synaptic knob

A swelling at the end of the presynaptic neurone. It has many mitochondria for ATP production, large smooth ER, voltage gated calcium channels

39

Synaptic cleft

Gap between the two neurones.
- 20 nm wide

40

Post synaptic membrane

-Specialised sodium channels
These have five polypeptides. Two for acetylcholine, with specialised receptors.

41

Acetylcholinesterase

An enzyme that is in synaptic cleft. It breaks down the transmitter substance acetylcholine. It hydrolyses it to ethanoic acid and choline. This stops the transmission of signals.

42

Hormones

Molecules released by endocrine glands directly into the blood. They act as messengers, carrying a signal to a specific target organ or tissue. There are two types, steriod and protein or peptide hormones.

43

Endocrine gland

A gland that secretes hormones directly into the blood. They have no ducts.

44

Exocrine gland

A gland that secretes molecules into a duct that carries the molecules to where they are used. They do no secrete hormones.

45

Adenyl cyclase

An enzyme associated with the receptor for many hormones, including adrenaline. It is found on the inside of the cell surface membrane.

46

Adrenaline.

A hormone released by the adrenal glands medulla. It is an amino acid derivative. Effects include: increased heart rate, increased stroke volume, vasoconstriction, increase mental awareness, dilate pupils, stimulate glycogenolysis

47

Steroid hormones

-Mineralocorticoids (e.g. aldosterone) help control sodium and potassium levels in blood
-Glucocorticoids (e.g. cortisol) help control the metabolism of carbohydrates and proteins in the liver

48

Pancreas

Lying below the stomach, it has endocrine and exocrine functions. It has a pancreatic duct which carries fluid to the small intestines. This fluid has amylase, trypsinogen and lipase. It is also alkaline.

49

Islets of Langerhans: alpha

Manufacture glucagon (hormone), which raises the blood glucose concetration.
+Glycogenolysis
+more fatty acids in respiration
+Gluconeogenesis

50

Islets of Langerhans: beta

Manufacture insulin (hormone), which lowers the blood glucose concentration
+More glucose enters cell
+Glycogenesis
+Glucose to fats
+More glucose for respiration

51

Glycogenolysis

Glycogen to Glucose

52

Gluconeogenesis

Amino acids and fats to Glucose

53

Glycogenesis

Glucose to Glycogen

54

Hyperglycaemia

State in which blood glucose concentration is too high

55

Hypoglycaemia

State in which blood glucose concentration is too low

56

Diabetes: Type I

Though to result from immune system attacking beta cells, and destroying them. Therefore insulin can no longer be produced, and excess glucose cannot become glycogen (glycogenesis). Normally treated by insulin injections.

57

Diabetes: Type II

Insulin can still be produced, but the responsiveness to insulin has declined. This could be because the receptors on the liver and muscle cells decline, or the insulin level may decrease. Factors causing early onset: obesity, high sugar diet, family history. Normally treated by lifestyle changes.

58

Myogenic tissue

Muscle tissue that can initiate its own contractions

59

Pacemaker

A region of tissue in the right atrium wall that can generate an impulse and initiates the contraction of the chambers

60

Medulla oblongata

Is found at the base of the brain. The region of the brain that coordinates the unconscious functions of the body such as breathing rate and heart rate

61

Cardiovascular centre

Specific region of the medulla oblongata that recieves sensory inputs about levels of physical activity, blood carbon dioxide concentrations and blood pressure. It sends nerve impulses to the SAN.

62

Accelerator nerve

Increases heart rate

63

Vagus nerve

Decreases heart rate

64

Heart rates factors

-Movement of limbs
-Exercise
-CO2 concentration
-Adrenaline
-Blood pressure

65

SAN

Sinoatrial node, region of tissue that can initiate an action potential, which travels as a wave over the atria walls