Topic 9 biology

homeostasis

homeostasis

the maintenance of a state of dynamic equilibrium in the body

sensors/receptors

specialised cells that are sensitive to specific changes in the environment

effectors

systems - usually muscles or glands - that either work to reverse

negative feedback systems

systems that provide a way of maintaining a condition within a narrow range. a change in conditions is registered by receptors and as a result effectors are stimulated to restore the equilibrium

positive feedback systems

systems where effectors work to increase an effect that has triggered a response

hormones

organic chemicals produced in the endocrine system and released into the blood and carried through the transport system to parts of the body where they bring about changes

endocrine glands

glands that produce hormones

exocrine glands

glands that produce chemicals and release them along small tubes or ducts

pituitary gland

a small gland in the brain that has an anterior and posterior lobe

hypothalamus

a small area of the brain directly above the pituitary gland that controls the activities of the pituitary gland and coordinates the autonomic nervous system

neurosecretory cells

nerve cells that produce secretions for mthe ends of their axons

cyclic AMP / cAMP

a compound formed from ATP that is produced when hormones such as adrenaline bind to membrane receptors and acts as a second messenger in cells

tropisms

plant growth responses to environmental cues

auxins

plant hormones that act as powerful growth stimulants and are involved in apical dominance

gibberellins

plant hormones that act as growth regulators

cytokinins

plant hormones that promote cell division in the apical meristems and the cambium through interactions with auxins

photomorphogenesis

the process by which the form and development of a plant is controlled by levels of and type of light

red light

has a wavelength of 580-660nm

far red light

has a wavelength of 700-730nm

phytochromes

a plant pigment that reacts with different types of light

short-day plants (SDP's)

plants that flower when days are short and nights are long

long-day plants (LDP's)

plants that flower when the days are long and nights are short

day-neutral plants (DNP's)

plants that are not affected by the length of time they are exposed to light or dark

florigen

a hypothetical plant hormone which is involved in the photoperiodic response.

etiolated

the form of plants grown in the dark

green fluorescent protein (GFP)

the product of a gene often used as a marker in the production of recombinant DNA

neurones

cells specialised for the rapid transmission of impulses throughout an organism

receptor cells

specialised neurones that respond to changes in the environment

effector cells

specialised cells that bring about a response when stimulated by a neurone

sense organs

groups of receptors working together to detect changes in the environment

central nervous system

a specialised concentration of nerve cells where incoming information is processed and from where impulses are sent out through motor neurons

axon

the long nerve fibre of a motor neurone which carries the nerve impulse

dendron

the long nerve fibre of a sensory neurone which carries the nerve impulse

peripheral nervous system

includes parts of the nervous system that spread through the body and are not involved in the central nervous system

nerve impulses

the electrical signals transmitted through neurones of the nervous system

dendrites

the slender

schwann cell

a specialised type of cell associated with myelinated neurones and forms the myelin sheath

myelin sheath

the fatty insulating layer around some neurones produced by the schwann cell

nodes of ranvier

the gaps between the schwann cells that enable salutatory conduction

polarised neurone

the condition of a neurone when the movement of positively charged potassium ions out of the cell down the conc gradient is opposed by the actively produced chemical gradient

resting potential

the potential difference across the membrane around 70mV when the neurone is not transmitting an impulse

neurotransmitter

a chemical that transmits an impulse across a synapse

sodium gates

specific sodium ion channels in the nerve fibre membrane that open up

depolarisation

the condition of the neurone when the potential across the membrane is briefly reversed during action potential

action potential

when the potential difference across the membrane is briefly reversed to +40mV on the inside

threshold

the point when sufficient sodium ion channels open for the rush of sodium ions into the axon to be greater than the outflow of potassium ions

refractory period

the time it takes for ionic movements to repolarise an area of the membrane and restore the resting potential after the action potential

absolute refractory period

the first millisecond or so after the action potential

relative refractory period

a period several milliseconds after an action potential when an axon may be re-stimulated

saltatory conduction

the process by which action potentials are transmitted from one node of ranvier to the next in a myelinated nerve

synapse

the junction between two neruones that nerve impulses cross via neurotransmitters

synaptic knobs

the bulges at the end of the presynaptic neurones where neurotransmitters are made

presynaptic membrane

the membrane on the side of the synapse where the first impulse arrives

synaptic vesicles

membrane bound sacs in the presynaptic knob that contain neuotransmitters and move to fuse with the presynaptic membrane when an impulse arrives

synaptic cleft

the gap between the pre and post synaptic membranes in a synapse

excitatory post-synaptic potential

the potential difference across the post-synaptic membrane caused by an influx of sodium ions

inhibitory post-synaptic potential

the potential difference cuased by an influc of negative ions as a result of neurotransmittors which makes the resting potential more negative

acetylcholine

a neurotransmitter found in the synapses of motor neurones

cholinergic nerves

nerves that use acetylcholine as the neurotransmitter in their synapses

noradrenaline

a neurotransmitter found in the synapses of the sympathetic nervous system and adrenergic synapses of the brain

adrenergic nerves

nerves that use noradrenaline as the neurotransmitter in their synapses

nicotine

a drug found in cigarettes that mimics the effect of acetylcholine and binds to specific acetylcholine receptors in post-synaptic membranes known as nicotine receptors

lidocaine

a drug used as a local anaesthetic that works by blocking the voltage-gated sodium channels in post-synaptic membranes in sensory neurones

cobra venom

a substance made by several species of cobra that binds reversibly to acetylcholine receptors in post-synaptic membranes in motor neurones

the brain

the area of the CNS where information can be processed and from where instructions can be issued as required to give fully coordinated responses to a whole range of situations

rods

photoreceptors found in the retina which contain the visual pigment rhodopsin

cones

photoreceptors found above the fovea of the retina which contain the visual pigment iodopsin

rhodopsin - visual purple

the visual pigment found in rods

spinal cord

the area of the CNS that carries the nerve fibres into and out of the brain and also coordinates many unconscious reflex actions

cerebrum

the area of the brain responsible for conscious thought

cerebral hemispheres

the two parts of the cerebrum joined by the corpus callosum

grey matter

consists of the cell bodies of neurones in the CNS

white matter

consists of the nerve fibres of neurones in the CNS

corpus callosum

the band of axons/white matter that join the left and right hemispheres together

hypothalamus

the area of the brain that coordinates the autonomic nervous system

cerebellum

the area of the brain that coordinates smooth movements

medulla oblongata

the most primitive part of the brain that controls reflex centres such as breathing

reflex responses

rapid responses that take place with no conscious thought involved

voluntary nervous system

involves motor neurones that are under voluntary or conscious control involving the cerebrum

autonomic nervous system

the involuntary nervous system that controls bodily functions that are not normally dealt with by conscious areas of the brain

sympathetic nervous system

involves autonomic motor neurones with very short myelinated preganglionic fibres that leave the CNS and synapse in a ganglion very close to CNS

parasympathetic nervous system

involves autonomic motor neurones

cardiac volume

the volume of blood pumped at each heartbeat

cardiac output

a measure of the volume of blood pumped by the heart per minute

cardiac control centre

found in the medulla oblongata

baroreceptors

the mechanoreceptors in the aorta and carotid arteries that are sensitive to pressure changes

chemoreceptors

sensory nerve cells or organs that respond to chemical stimuli

osmoregulation

the maintenance of a constant osmotic potential in the tissues of living organisms by controlling water and salt concentrations

deamination

the removal of an amino group from excess amino acids in the ornithine cycle in the liver

ornithine cycle

the series of enzyme controlled reactions that convert ammonia from excess amino acids into urea in the liver

ultrafiltration

the process by which fluid is forced out of the capillaries in the glomerulus of the kidney into the kidney tubule through the epithelial walls of the capillary and capsule

selective reabsorption

the process by which substances needed by the body are reabsorbed from the kidney tubules into the blood

tubular secretion

the process by which inorganic ions are secreted into or out of the kidney tubules as needed to maintain the osmotic balance of the blood

nephrons

microscopic tubules that make up most of the structure of the kidney

proximal convoluted tubule

the first region of the nephron after bowman's capsule

counter current multiplier

a system that produces a concentration gradient in a living organism using energy from cellular respiration

distal convoluted tube

the section of the nephron after the loop of henle that leads to the collecting duct

antidiuretic hormone

a hormone produced in the hypothalamus and stored in the posterior pituitary that increases the permeability of the distal convoluted tube and the collecting duct to water

collecting duct

takes urine from the distal convoluted tubule to be collected in the pelvis of the kidney

osmoreceptors

sensory receptors in the hypothalamus that detect a change in the concentration of inorganic ions