Biology Paper 2

Define stimulus

A change in the environment

Define receptor

A specialised cell that detects a stimulus and generates a nerve impulse

What are dendrites?

Extensions of the cytoplasm to increase surface area for electrical impulses

What does the myelin sheath do?

Wraps around the axon and insulates the nerve signal to increase the rate of transmission

What is the difference between a neurone and a nerve?

A neurone is one cell, a nerve is a collection of nerve cells

Define synapse

junction between two neurons

What is the function of the sensory neurone?

Caries impulses from receptor cells to the CNS

What is the function of the relay neurone?

Carries electrical impulse from sensory neurone to motor neurone through the CNS

What is the function of the motor neurone?

carry impulses from CNS to effector

Name the two effectors

muscles and glands

What is the axon?

A long thin extension of the cytoplasm of a neurone

Which effector contracts to cause movement?

Muscles

What is the largest part of the brain called?

Cerebral cortex

What is the cerebral cortex responsible for?

memory, thought, sight, speech etc

What does the hypothalamus do?

maintains homeostasis

Where is the thermoregulatory centre?

hypothalamus

What is the master gland?

Pituitary gland

What does the medulla control?

heart rate and breathing

What does the cerebellum do?

Balance and coordination

Is the cerebellum in the front or the back of the brain?

Back

What does the retina contain?

rods and cones (photoreceptors)

What is the tough outer layer of the eye?

Sclera

What is the sclera?

The tough outer layer that protects the eye

What does the cornea do?

Refracts light into the eye

What is the transparent and curved layer at the front of the eye called?

The cornea

What is the iris?

A ring of muscle in the eye that controls how much light enters the eye

What do the ciliary muscles do?

change the shape of the lens

What do the suspensory ligaments do?

hold the lens in place

What happens to the muscles in the eye in dim light?

Pupil dilates

Radial muscles contract

Circular muscles relax

More light enters

What happens to the muscles in the eye in bright light?

Pupil constricts

Circular muscles contract

Radial muscles relax

Less light enters

Dim or bright light: pupil dilates?

Dim light

Dim or bright light: pupil constricts?

Bright light

Dim or bright light: radial muscles contract?

Dim light

Dim or bright light: circular muscles contract?

Bright light

What happens to the suspensory ligaments when the eye focusses on near objects?

They loosen

What happens to the suspensory ligaments when the eye focusses on far objects?

Tighten

Define myopia

Short sightedness

Define hyperopia

Long sightedness

Where do the light rays focus for someone with myopia?

In front of the retina

Where do the light rays focus for someone with hyperopia?

Behind the retina

What can cause myopia?

lense is too rounded or eye is too long

What can cause hyperopia?

lense is too flat or eye is too short

What treats myopia?

Concave lens

What treats hyperopia?

Convex lens

What is the ideal body temperature?

37°C

Define homeostasis

keeping internal body conditions relatively constant involving small fluctuations around a set level

Define endotherm

Internal physiology regulates body temperature

Define ectotherm

External behaviour regulates body temperature

What is responsible for regulating our body temperature?

Hypothalamus

Which two structures refract (bend) light entering the eye?

cornea and lens

Where in the brain is the medulla found?

brain stem

When the pupil is very large, do we describe it as 'constricted' or 'dilated'?

dilated

When the eye is exposed to bright light, will the pupil constrict or dilate?

constrict

When light passes into the eye, where on the retina should the light be focused?

the fovea

What is the purpose of the iris reflex?

To ensure the optimum amount of light enters the eye

Where is the medulla located?

brain stem

Do cone or rod cells allow you to see colour?

Cone cells

Which light sensitive cells in the retina enable you to see in the dark?

Rod cells

Define hormones

Small chemical molecules that are excreted by glands into the bloodstream

Name the 6 main glands in the endocrine system

Pituitary Gland,

Thyroid Gland,

Adrenal Glands,

Pancreas,

Testes (male only),

Ovaries (female only)

Where are the adrenal glands located?

above the kidneys

Endocrine or nervous: relies on hormones

Endocrine

Endocrine or nervous: effects last longer

Endocrine

Endocrine or nervous: more localised effect

Nervous

What gland excretes insulin?

Pancreas

What gland excretes oestrogen?

Ovaries

What gland excretes Thyroxine?

Thyroid

What gland excretes ADH?

Pituitary gland

What gland excretes adrenaline?

Adrenal glands

What is the target organ of insulin?

liver

What is the target organ of oestrogen?

Ovaries, uterus, pituitary gland

What is the target organ of ADH?

kidneys

What does ADH stand for?

antidiuretic hormone

What does ADH control?

water balance

What does thyroxine control?

metabolic rate

Which organ detects a change in blood sugar levels?

pancreas

Which hormone decreases blood glucose levels?

insulin

What are the two main organs that insulin stimulates to absorb glucose from the blood?

the liver and muscles

What hormone is released when blood glucose levels are too high?

Insulin

What hormone is released when blood glucose levels are too low?

Glucagon

What does insulin do in the muscle and liver cells?

Converts glucose to glycogen

What does glucagon do in the muscle and liver cells?

Converts glycogen to glucose

Which type of diabetes is insulin dependant?

Type 1

Which type of diabetes is insulin resistant?

Type 2

How could type 1 diabetes be described?

Insulin dependant

What causes high blood glucose levels in someone with type 1 diabetes?

No insulin is produced so glucose is not absorbed into cells

What causes high blood glucose levels in someone with type 2 diabetes?

Insulin does not fit with the receptors so more and more is released to try to lower the levels

Why does someone with diabetes lose more water than an "healthy" person?

The higher concentration of glucose in the blood creates a large concentration gradient from the blood to the more dilute cells, so water moves by osmosis out of the cells into the blood more easily and faster.

Glucose is a type of:

carbohydrate

What happens if there is too little thyroxine in the body?

TSH is produced

What is excess glucose in the body converted into?

glycogen

What are two ways that ions can be removed from the body?

Sweating

The Kidneys

What are nephrons?

Filtration units in the kidneys

Which part of the brain detects the level of water in the body?

hypothalamus

Where does blood enter the kidneys?

renal arteries

Where does blood exit the kidneys?

renal vein

How much urea is selectively reabsorbed?

none

How many ions are selectively reabsorbed?

It depends on how many we already have in the blood

Where is urine excreted from?

urethra

What are the treatments for kidney failure?

dialysis or kidney transplant