Coordination and response Flashcards
Accomodation
The process by which the elastic lens changes its shape (with the aid of ciliary muscles and suspensory ligaments) to focus on near or distant objects. Light is focused onto the retina
Adrenal glands
Endocrine glands located above the kidneys that produce adrenaline
Adrenaline
A hormone produced by the adrenal glands that is involved in the fight or flight response. It increases heart rate, breathing rate and widens pupils. Adrenaline also increases blood glucose concentration
Antagonistic muscles
Pairs of muscles that work in an opposing fashion eg. circular and radial muscles
Auxins
A group of plant hormones that stimulate growth in shoot tips. They are involved in plant tropism
Blind spot
The area at the back of the eye where the optic nerve exits the eye. It lacks receptor cells so cannot detect an image.
Central nervous system (CNS)
The brain and spinal cord
Ciliary muscle
A ring of smooth muscle that controls the shape of the lens
Circular muscles
Muscles of the iris that are involved in the pupil reflex action. In bright light, the circular muscles contract to constrict the pupil. Less light enters the eye.
Cone cells
Cells found in the retina that are sensitive to high light intensity (bright light). There are three types of cone cells that can detect light of diffrent colours
Cornea
The transparent outer covering of the eye which refracts light entering the eye. A clear layer which coats the iris
Effector
An organ, tissue, or cell that produces a response to stimulus
Endocrine glands
Glands of the endocrine system that secrete hormones directly into the bloodstream
Endocrine system
A collection of glands that secrete hormones into the bloodstream. Transmission of signals is slow and the effects are long lasting.
Fovea
A region in the middle of the retina with a high density of cone cells. This section provides the clearest image
Glucagon
A hormone secreted by the pancreas when blood glucose levels are too low. It causes the breakdown of glycogen into glucose in the liver.
Gravitropism
The plant’s growth in response to gravity
Hair erector muscles
Tiny muscles found in the skin which contract causing hairs to stand erect
Homeostasis
The maintanance of a stable internal environment in the body (within set limits) despite flunctuations in internal and external conditions. Allows an environment for cells to function
Hormone
A cell signaling molecule produced by endocrine glands and released into the blood. It travels to a target organ and binds to receptors on effectors, initiating a response
Hypothalamus
A structure in the brain that contains the thermoregulatory centre. It coordinates information from the receptors and sends instructions to the effectors
Insulin
A hormone secreted by the pancreas when blood glucose concentration is too high. It causes liver and muscle cells to increase their uptake of glucose and the conversion of glucose to glycogen in the liver
Involuntary action
An action that does not involve conscious thought. Also known as a reflex action
Iris
A pigmented ring of circular and radial muscles. It controls the size of the pupil to alter how much light enters the eye
Lens
The transparent structure behind the iris. focusing it onto the retina. The lens is attached to a ring of ciliary muscle via suspensory ligaments
Motor neurone
A neurone that carries nerve impulses from CNS to the effectors
Negative feedback
A corrective mechanism that allows only small shifts from a set point, reversing a change in conditions
Negative plant tropism
The growth of a plant away from a stimulus
nerve impulse
An electrical signal that travels along neurones
Nervous system
A collection of nerves and neurones involved in the transmission of electrical impulses. Transmission of signals is rapid and the effects are short lived
Neurone
A specialised cell that transmits nerve impulses. Transmission of signals is rapid and the effects are short lived
Neurotransmitter
Chemicals that are used for communication between neurones and their target cells. Neurotransmitters are stored in synaptic vesicles in the presynaptic neurone and released into the synaptic cleft
Oestrogen
A female sex hormone released by the ovaries that is involved in the development of the female secondary sexual characteristics. It also causes the growth and repair of the uterus lining during the menstrual cycle.
Optic nerve
A nerve at the back of the eye that transmits nerve impulses to the brain from the retina
Ovaries
A pair of endocrine glands in females that secrete oestrogen into the bloodstream
Pancreas
An endocrine gland situated behind the stomach that produces insulin
Peripheral nervous system
Pairs of nerves that originate from the CNS and carry nerve impulses into and out of the CNS
Phototropism
A plant’s growth response to light
Plant tropism
The growth response of a plant to a stimuli
Positive plant tropism
The growth of a plant towards a stimulus
Pupil
The aperture of the iris through which light rays enter the eye
Pupil reflex
a type of reflex action. The size of the pupil changes in response to exposure of the eye to different light intensities. Pupil size is controlled by the antagonistic circluar and radial muscles in the iris
Radial muscles
Muscles of the iris that are involved in the pupil reflex action. In dim light, the radial muslces contract to dilate the pupil.
Receptors
A specialised structures that detects a specific type of stimulus
Reflex
A rapid, automatic response to a sensory stimulus in the body. It serves as a protective mechanism
Reflex arc
The pathway of neurones involved in a reflex action
1. Stimulus
2. Receptor
3. Sensory neurone
4. Relay neurone
5. motor neurone
6. effector
7. response
Relay neurone
A neurone located in the spinal cord that links the sensory neurone to the motor neurone. Relay neurones are short and have a small cell body at one end with many dendrites branching off it.
Retina
A specialised layer at the back of the eye composed of light receptors (photoreceptors). It converts light energy into neural signals which are sent to the brain via the optic nerve
Rod cells
Cells in the retina that are sensitive to low light intensity (dim light)
Sense organ
A group of specialised receptor cells that respons to certain stimuli. The five sense organs are the eyes, ears, nose, skin and tongue
Sensory neurone
A neurone that carries nerve impulses from the receptors to the CNS. Sensory neurones are long and have a cell body branching off the middle of the axon
Shivering
The involuntary contraction of muscles which generates heat from respiration
Stimulus
A change in an organisms internal or external environment that can be detected
Suspensory ligaments
A seiries of fibres that attach the lens to a ring of ciliary muscle
Sweat glands
Small tubular structures that secrete sweat onto the surface of the skin
Sweating
The secretion of sweat onto the surface of the skin by sweat glands
Synapse
The junction between two nerve cells or a nerve cell and an effector that ensures nerve impulses can travel in one direction only
Synaptic cleft
A small gap between neurones across which a nerve impulse is transmitted via neurotransmitters
Synaptic vesicles
Secretory vesicles located in the presynaptic neurone that store
neurotransmitters and release them into the synaptic cleft on arrival of a nerve
impulse.
Testes
A pair of endocrine glands in males which secrete testosterone into the
bloodstream.
Testosterone
A male sex hormone released by the testes that is involved in the
development of the male secondary sexual characteristics.
Thermoregulatory centre
An area of the hypothalamus that regulates body
temperature. It contains receptors sensitive to blood temperature.
Type 1 diabetes
A type of diabetes in which the pancreas fails to produce enough
insulin. It is controlled using daily insulin injections, limiting refined sugar intake and
getting regular exercise.
Vasoconstriction
Constriction of arterioles near the surface of the skin. Less blood
flows close to the skin surface, decreasing heat loss to the surroundings.
Vasodilation
Dilation of arterioles near the surface of the skin. This allows blood to
flow closer to the skin surface, increasing heat loss to the surroundings.
Voluntary action
An action that involves conscious thought.
controlled movement and autonomic reflexes are carried out by
The bodys central nervous system (CNS)
how does the nervous system coordinate and regulate body functions?
By sending electrical signals known as nerve impulses
two main sections of nervous system
Central nervous system (CNS) and peripheral nervous system (PNS)
CNS: Brain and spinal cord
PNS: Nerves outside the brain and spinal cord which carry impulses to and from CNS
Sensory neurone
Carries impulses from a receptor to the spinal cord and brain
Relay (connector) neurone
Carries impulses between diffrent parts of the CNS
Motor (effector) neurone
Carries nervous impulses from the central nervous system to the effector eg. a muscle. Motor neurones are long and have a large cell body at one end with long dendrites branching off it.
Involuntary movement
Automatic reflexes organisms carry out when they are in danger. This is known as reflex action. The nervous impulse does not travel to the brain.
Reflex arc
- A stimulus such as heat from a flame is detected by receptors
- The receptor sends an impulse down the sensory neurone to the spinal cord
- The relay neurone in the CNS passes the impulse to the motor neurone.
- The impulse travels along the motor neurone to and effector (eg. a muscle), which reacts to remove the organism from danger
Synapse
A junction between two neurones.
Explain a synapse
The synapse forms a gap called a synaptic cleft between the presynaptic neurone and the postsynaptic neurone. When an impulse arrives at the presynaptic neurone, vesicles in the neurone fuse with the membrane, releasing neurotransmitters into the synaptic cleft. The neurotransmitters diffuse across the synapse, binding to receptors on the postsynaptic neurone. This triggers a nervous impulse in the postsynaptic neurone, so the impulse can be transmitted to the other parts.
What to synapses ensure?
They ensure undirectionality of nervous impulses, as the vesicles containing the neurotransmitter are only present in the presynaptic neurone, whilst the receptors are only present in the postsynaptic neurone, the impulse cannot travel backwards
What are sense organs?
A group of receptor cells which respond to a specific stimulus. The eye is a sense organ which responds to light. Other sense organs may respond to temperature, touch, sound and chemicals
Optic nerve
Each photoreceptor cell is attached to a neurone. These neurones group together to form the optic nerve, which carries the impulse to the brain
Pupil reflex
The pupil of the eye can expand and contract to control the amount of light that enters the eye. This action is carried out by two sets of muscles, radial and circular, which work antagonistically.
Pupil reflex at low light intensities
The pupil dilates to allow more light to enter the eye by relaxing the circular muscles and contracting the radial muscles.
Pupil reflex at high light intensities
The pupil constricts to limit the amount of light entering the eye by relaxation of the radial muscles and contraction of the circular muscles. This is to prevent the eye being damaged by the bright light.
How is accomodation carried out?
The eye can docus on both near and far objects. This is achieved by changing the shape of the lens, which is controlled by ciliary muscles and suspensory ligaments.
Name two types of photoreceptor cells
Rods and cones
Distribution and function of rod cells
Rod shaped, used for monochromatic night vision as they are more sensitive to low levels of light. Evenly distributed at the periphery of the retina; absent at the fovea
Distribution and function of cone cells
Cone shaped, used for colour vision in bright light. There are three types of cone cells, each sensitive to a diffrent colour (red, green and blue). Concentrated at the fovea
What does the endocrine system produce
The endocrine system produces and secretes hormones. Which are chemical substances that travel in the blood and are used for signalling in the body. They are produced in the glands such as pituary and adrenal glands, before being secreted in the blood where they travel to target organs and cause a change in cells
Endocrine glands
A network of hormone secreting glands, form the endocrine system. They help control growth metabolism and homeostasis, among other functions
Name four endocrine glands
Adrenal glands (located at top of kidney)
Pancreas, Testes, Ovaries
Why are nervous impulses faster than hormones
Hormones must be transported in the blood while nervous impulses can travel along specialised nerve cells
The endocrine system uses chemicals (hormone) whereas the nervous system uses electrical signals
Why do internal conditions need to be maintained?
Internal conditions must be maintained between set limits, if these limits exceed, negative feedback mechanisms work to correct the change and restore the internal environment to the optinum
What happens when blood glucose levels are too high?
If the level of glucose in blood is too high, the water potential of the blood becomes very low, water moves out of cells into the blood by osmosis. This leads to cells shrinking and eventually dying
What happens when blood glucose levels are too low
If the level is too low, water potential is high and thus water moves from blood into cells, causing them to lyse.
Hormones used to regulate blood sugar levels
Glucagon and Insulin
Which hormone is released when glucose levels are too high
If a blood-glucose concentration is too high, this will be detected by the pancreas. The
pancreas secretes Insulin into the blood. Insulin causes glucose to be converted to
glycogen in the liver. It also causes more glucose molecules to diffuse into cells from
the blood, lowering the amount of glucose in the blood.
Which hormone is released when glucose levels are too low
Glucagon is released when blood-glucose concentration is too low. Glucagon inhibits
glucose being converted to glycogen in the liver and activates an enzyme that converts
glycogen to glucose, making more glucose available to cells. It also decreases the
respiratory rate in cells so that less glucose is used in respiration.
People with diabetes cannot produce insulin
Type 1 diabetes
Type 1 diabetes is caused by an autoimmune
response in which antibodies attack cells in the pancreas which usually make insulin. This
means that no insulin can be produced. Type 1 diabetes is usually treated by patients injecting insulin themselves.
Type 2 diabetes
In type 2 diabetes, either not enough insulin is produced by the pancreas, or the cells do not respond correctly to the insulin.
Why is it important to maintain a body temperature of 37C
Optium temperature for enzyme reactions. If the temperature is lower, the rate of the reaction would decrease so reactions would take longer to occur. If it was too high, the enzymes may denature and prevent reactions from occuring.
What regulates body temperature
The temperature is regulated by the hypothalamus in the brain, which contains thermoreceptors. If the temperature moves away from the optimum, a response is triggered to return the temperature to the optimum.
Reactions to a low internal temperature
Shivering- muscles contract to produce heat.
Vasoconstriction- blood vessels constrict to reduce surface area and move away from the surface of the skin to reduce heat loss
Reactions to a high internal temperature
Sweating- sweat evaporates from the skin, reducing surface temperature
Vasodilation- Blood vessels dilate, causing more heat loss to the environment.
Tropisms
Growth movements in plants that occur in reaction to external stimuli. Plants can show positive or negative response.
Phototropism
A response to light. Plant shoots are positively phototrophic, as they move towards light in order to allow the plant to absorb more light to photosynthesize. Plant roots are negatively phototropic as they move away from light.
Phototropic response
- Auxins are produced in the shoot tips, which are then transported down the shoot
- Light causes auxins to move to the shady side of the shoot
-The auxin causes cell elongation on the shady side - The cells grow faster on the shaded side, thus the shoot bends towards the light
Gravitropism
Gravitropism (also known as geotropism) is a response to gravity. Shoots are negatively gravitropic, as they grow upwards against gravity, whereas roots are positively gravitropic
A bundle of neurones is known as a
nerve
Electrical signals that pass along nerve cells are known as
Neurones
Why is less time required to transfer an impulse from one cell to another?
Neurones have a long fibre. The axon is insulated by a fatty sheath with small uninsulated sections (nodes). Electrical impulses don’t travel down the whole axon but jumps from one node to the next. Their body contains many extensions called dendrites. This means they can connect to many other neurones and receive impulses from them, forming a network for easy communication.
