Homeostatis

Question 1

Def of homeostasis

Answer 1

Physiological control systems maintain the internal environment within restricted limits

Question 2

Why is homeostasis important for organisms

Answer 2

Homeostasis is important
1. Maintains optimum conditions for enzyme action and cellular function

Question 3

Examples of physiological factors controlled by homeostasis

Answer 3

1. Core body temperature
2. Metabolic waste concentrations (urea + CO2)
3. Blood pH
4. Concentration of glucose in blood
5. Water potential of the blood
6. Concentration of respiratory gases in blood

Question 4

What is a hormone

Answer 4

Chemical substance released by endocrine glad that is carried by the blood to stimulate an effect on target organ

Question 5

Compare endothermic and ectotherms

Answer 5

Endotherms
- warm blooded
- heat from the inside

Ectotherms
- cold blooded creatures
- heat themselves by environmental conditions

Question 6

Where does body heat energy come from in endotherms

Answer 6

Externally
- mammals absorb solar radiation directly, or indirectly by radiation, conduction or convection from their environment

Internally
- as by product of metabolic rate, respiration

Question 7

Outline the role of hypothalamus in thermoregulation

Answer 7

Thermoregulation centre in hypothalamus initiates switching on/off heat loss/ conservation mechanism
(Two centres: hot control + cold control)
Thermoreceptors (heat sensitive neurones) monitor temperature

Question 8

What is negative feedback

Answer 8

When a change occurs in body it responds in such a way as to reverse the direction of change

Question 9

Mechanism for negative feedback

Answer 9

1) sensory receptor detects change (stimulus)
2) an integrating centre receives input from sensors and coordinates the response
3) effector carry out corrective actions to bring about a response
4) returning conditions to normal is negative feedback

Question 10

Annotate diagram on the control of body temperature

Answer 10

See notes

Endothermic animals detect external temperatures via peripheral receptors; these are thermoreceptors found in the skin and mucous membranes
Receptors detect heat and cold
Impulses are sent from the receptors to the hypothalamus
The hypothalamus also contains receptors that monitor the temperature of the blood flowing through it
Information from the receptors is processed by the hypothalamus, which then initiates homeostatic responses when temperature gets too high or too low
Human skin contains a variety of structures that are involved in the regulation of heat loss

Question 11

Advantages and disadvantages of being ectotherm (cold blooded)

Answer 11

ADV:
- less food needed
- greater proportion of food energy for growth
DISADV:
- less active in cooler temperatures as need to warm up before can be active

Question 12

Advantages and disadvantages of being an endotherm (warm blooded)

Answer 12

ADV:
- can be active in cooler conditions
- enzymes can work efficiently all the time
- can inhabit at cooler regions
DISADV:
- significant proportion of food intake used to generate heat
- less food energy available for growth

Question 13

Types of peptide hormones and steroid hormones

Answer 13

PEPTIDE
- adrenaline
- insulin
-glucagon

STEROID
- oestrogen
- Progesterone

Question 14

What is the normal blood concentration of glucose

Answer 14

90mg/100cm3

Question 15

Symptoms of too low sugar levels

Answer 15

Respiration slows which reduces formation of ATP
Stops cellular processes
Brain cells die leading to fainting then death

Question 16

Symptoms of glucose levels in blood being too high

Answer 16

The blood water potential drops leading to cells losing water causing organ damage and failure leading to death in serve cases

Question 17

What is the role of the pancreas

Answer 17

In exocrine system (enzymes)
- produces enzymes in pancreatic duct for digestion
In endocrine system (hormones)
- islets of langerhans secrete hormones insulin & glucagon directly to blood stream to regulate glucose levels

Question 18

What happens to glucose in muscle/adipose and liver tissue

Answer 18

In Muscle/adipose tissue
- increase uptake due to increase glucose channels
M —> glycogen. A —> Fat

In liver tissue
- increase uptake increased diffusion
Converted glycogen or respired

Question 19

Process of lowering blood glucose levels in muscle or adipose cells

Answer 19

1) insulin binds to receptors
2) binding causes chemical signal inside cell
3) chemical signal effects vesicle causing it to fuse with membrane and release glucose carrier proteins onto membrane
4) increase the number of glucose carrier proteins
5) facilitated diffusion of glucose into cell increases
6) enzymes activated to turn glucose —> glycogen (muscle cell) or fat (adipose cell)

Question 20

Annotate insulin effect on muscle/ adipose cell diagram

Answer 20

Include
- insulin binding to receptors
-vesicle with glucose carrier proteins
- glucose carrier proteins onto membrane
- enzymes with glucose Turing to fat or glycogen

Question 21

Process of lowering blood glucose levels in liver cells

Answer 21

1) insulin binds to receptors proteins
2) chemical signal activates enzyme - phosphorylase
3) this reacts glucose with phosphate (phosphorylises)
4) this maintains conc gradient increasing uptake of glucose by diffusion
5) other enzymes stimulated which causes glycolysis and glycogenesis to occur

Question 22

Outline glucagon’s role in increasing blood glucose levels

Answer 22

• activation of enzymes in the liver
  Which increases glycogen breakdown (glycogenolysis)
  Glucose synthesised from lactate and amino acids (gluconeogenesis)

Question 23

Def of glycogenolysis

Answer 23

The process of glycogen breakdown into glucose

Question 24

Def of gluconeogenesis

Answer 24

The process of glucose being synthesised from lactate and amino acids

Question 25

What is the role of adrenaline in increasing blood glucose levels

Answer 25

Adrenaline affects the liver - uses a second messenger cAMP - increases glycogen breakdown (glycogenolysis) - also inhibits enzyme glycogen synthase preventing production on glycogen so more glucose available

Question 26

What is secondary messenger system

Answer 26

Used by many hormones It works to use 1 hormone molecule - to produce many cAMP molecules - and large amounts of enzymes To causes response

Question 27

Annotate summary of glucose control

Answer 27

See notes Too low 1. Alpha cells detect fall, glucagon secretion, in liver glycogen breakdown and synthesis of glucose Too high Beta cells detect rise, insulin secretion, increased uptake of glucose by adipose cells, muscle cells and liver tissue

Question 28

Information of the 1 diabetes

Answer 28

1) T-cells attack beta cells in pancreas decreasing insulin secreted 2) liver doesn’t store glycogen - cannot replace glucose quickly - neurones can only respire glucose to levels falls = coma 3) cells don’t take up glucose after meal - glucose can rise too high affecting brain cells 4) treated with insulin - injected or digested if taken orally

Question 29

Info on type 2 diabetes

Answer 29

- associated with obesity/ unbalanced diets - receptors stops responding to insulin Beta-cells produce more If beta cells become damaged type 1 diabetes can develop - can’t be treated with insulin

Question 30

Function of the renal artery

Answer 30

Carry blood from abdominal aorta to kidneys

Question 31

Function of renal veins

Answer 31

Drains blood from the kidney into inferior vena cava

Question 32

Label the diagram of kidney

Answer 32

Include - outer area = cortex - outer layer = renal capsule - inner part = medulla - nephron - renal vein - renal artery - renal pelvis - ureter

Question 33

Label structure of nephron ( in kidney)

Answer 33

Include - efferent arteriole - afferent arteriole - bowman’s capsule - glomerulus - distal tubule - collecting duct - loops of Henle (ascending & descending) - peritubular capillaries - proximal tubule

Question 34

Role of efferent arteriole in nephron of kidney

Answer 34

Tiny artery that carries blood out of glomerulus

Question 35

Role of afferent arteriole in nephron of kidney

Answer 35

Tiny artery carries blood to nephron & into glomerulus

Question 36

Role of bowman’s capsule in nephron of kidney

Answer 36

End of tubules that surround the glomerulus

Question 37

Role of glomerulus in nephron of kidney

Answer 37

Network of capillaries that is the site of ultrafiltration

Question 38

Role of distal tubule in nephron of kidney

Answer 38

1. Regulation of Electrolyte Balance The distal tubule fine-tunes the reabsorption of ions like sodium (Na⁺), calcium (Ca²⁺), and chloride (Cl⁻). Sodium reabsorption is influenced by the hormone aldosterone, which increases sodium uptake and helps maintain blood pressure. 2. Acid-Base Balance It helps regulate the body's pH by secreting hydrogen ions (H⁺) into the filtrate and reabsorbing bicarbonate (HCO₃⁻), ensuring blood pH remains within a healthy range. 3. Water Reabsorption The distal tubule's permeability to water is regulated by the hormone antidiuretic hormone (ADH). When ADH levels are high, more water is reabsorbed, concentrating the urine. 4. Dilution of Urine The distal tubule contributes to making the urine more dilute by reabsorbing solutes without reabsorbing water (in the absence of ADH

Question 39

Role of collecting duct in nephron of kidney

Answer 39

Collects urine made by nephron and channels it into the minor calyx

Question 40

Role of the loop of Henle in nephron of kidney

Question 41

Role of peritubular capillaries in nephron of kidney

Answer 41

Capillaries that surround the tubules and exchange water and solutes within it

Question 42

Role of proximal tubule in nephron of kidney

Answer 42

selective reabsorption of vital substances from the glomerular filtrate back into the bloodstream

Question 44

Function of

Question 45

Ways in which endotherms decrease body temp

Answer 45

Vasodilation During vasodilation the muscles in the walls of arterioles relax, causing dilation and allowing more blood to flow into skin capillaries Heat is lost to the environment by radiation Sweating Sweat is secreted by sweat glands in the skin This cools the skin by evaporation Heat energy from the body is used to convert liquid water into water vapour Sweating is less effective as a cooling mechanism in humid environments there is a reduced water vapour concentration gradient between the skin and the air when humidity is high Flattening of hairs The hair erector muscles in the skin relax, causing hairs to lie flat This stops them from forming an insulating layer of air and instead allows air to circulate over skin, removing heat lost by radiation

Question 46

Way in which endotherms increase body temp

Answer 46

Vasoconstriction During vasoconstriction the muscles in arteriole walls contract, causing the arterioles near the skin to constrict and allowing less blood to flow through skin capillaries Instead, the blood is diverted through shunt vessels, which are deeper in the skin and therefore do not lose heat to the environment Heat loss by radiation at the skin surface is reduced Increased metabolic rate Most of the metabolic reactions in the body are exothermic and this provides warmth to the body In cold environments the hormone thyroxine increases the basal metabolic rate (BMR), increasing heat production in the body Thyroxine is released by the thyroid gland Shivering Muscles contract and relax repeatedly in quick succession The metabolic reactions required to power this muscle contraction releases heat energy to warm the blood and raise the core body temperature Erection of hairs The hair erector muscles in the skin contract, causing hairs to stand on end This traps an insulating layer of air over the skin's surface, reducing heat loss by radiation