9. Co-ordination and Response in Humans Flashcards
state what is a stimulus, a receptor, and function of CNS [3]
- Stimulus is a change in the environment which is
detected by receptors - Receptor will produce nerve impulses to send to the central nervous system by neurones
- CNS then transmits nerve impulses to the effector to react to the changes in surroundings
state the principal component parts of the eye in producing a focused image of near and distant objects on the retina (7)
- cornea
- aqueous humour
- lens
- retina
- optic nerve
- ciliary muscles
- suspensory ligaments
describe the pupil reflex in response to bright light (3)
- Circular muscles of the iris contract
- Radial muscles of the iris relax
- The pupil becomes smaller or constricts, reducing the amount of light entering the eye
describe the pupil reflex in response to dim light (3)
- Radial muscles of the iris contract
- Circular muscles of the iris relax
- The pupil enlarges or dilates, increasing the amount of light entering the eye.
outline the functions of motor neurones
Transmit nerve impulses from the CNS to the
effector muscle cells or gland cells
define hormone
a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver
describe a reflex arc (5)
- Receptors in the skin detect the stimulus such as pricked by a needle or touching a hot object
- Nerve impulses are produced which are transmitted by the sensory neurone to the spinal cord.
- In the spinal cord, the nerve impulses are transmitted across a synapse to a relay neurone and then across another synapse to the motor neurone.
- Nerve impulses travel along the motor neurone to the motor end plate, then the effector
- The effector muscles contract causing the hand to withdraw
define hormone
a chemical substance, produced by endocrine gland, carried by the blood, which alters the
activity of one or more specific target organs and is then destroyed by the liver
state what is meant by an endocrine gland, with reference to the islets of Langerhans in the pancreas (3)
- define endocrine gland
- difference of endorine and exocrine and example
- other examples ( list 2)
Endocrine glands are glands that secrete their products directly into the bloodstream (our focus)
Some glands are both exocrine and endocrine, eg pancreas, which
secretes pancreatic juice via the pancreatic duct, and also secretes the hormone insulin and glucagon from the islets of Langerhans directly into the bloodstream.
Other examples of endocrine glands that secrete hormone is as below:
• Pituitary gland secretes antidiuretic hormone (ADH)
• Hypothalamus regulates the secretion of some pituitary hormones.
• Adrenal gland secretes adrenaline.
• Pancreas islets of Langerhans secrete insulin and glucagon.
• Testis (in males) secretes testosterone.
• Ovary (in females) secretes oestrogen and progesterone
outline how the blood glucose concentration is regulated by insulin
point 1 (1)
point 2 (1)
point 3 (4)
- When blood glucose
level increases beyond the norm, more insulin
is released by islets of Langerhans in
pancreas to the
bloodstream - Blood transport insulin to the effector cells which are muscles cells and liver cells
- Insulin decreases blood glucose concentration by:
• Stimulating body cells to increase glucose uptake by
increasing permeability of plasma membranes to glucose
• Stimulating the liver and muscle cells to store glucose in the form of glycogen
• Decreasing glycogen breakdown in the liver
• Decreasing the conversion of fatty acids and amino acids
to glucose in the liver
outline how the blood glucose concentration is regulated by glucagon
- point 1 (1)
- point 2 (1)
- point 3 (3)
- When blood glucose level falls below the
norm, more glucagon is released by islets of
Langerhans in pancreas to the bloodstream - Blood transports glucagon to the effector cells which are liver cells
- Glucagon increases blood glucose concentration by
stimulating liver cells to:
• Convert stored glycogen in liver to glucose
• Convert amino acids and fatty acids to glucose
• Convert lactic acid into glucose
function of lens (2)
• Transparent biconvex structure that refracts light onto the retina.
• The lens can change its curvature to focus light onto retina
function of retina
Innermost layer of the eyeball which contains photoreceptors, which are connected to the optic nerve
function of optic nerve (2)
• Transmits signal from the retina to the brain.
• There are no photoreceptors in the area of the retina where the optic nerve leaves.
This area is called the blind spot
function of ciliary muscles
Contains ciliary muscles which control the curvature of the lens. It is also
responsible for producing aqueous humour.
