Unit 6 - Organisms respond to changes in their environments Flashcards
Nodes of ranvier
Between the Schwann cells.
Used in action potential and speed up the impulse.
Saltatory conduction
The propagation of actions potentials along a myelinated neurone from one node of ranvier to the next.
Factors that affect impulse speed
- Myelination increases the speed of impulse transmission due to saltatory conduction.
- The wider the axon the greater the speed of conduction.
- The higher the temperature the greater the transmission speed due to faster diffusion of ions.
Dendrons
Extensions of cells body which divide into dendrites.
Carry nerve impulses towards cell body.
Axon
Long single fibre that carries nerve impulses away from cell body.
Schwann cells
Surround axon, protect and insulate it. Carry out phagocytosis and form the myelin sheath.
Repolarisation
Membrane becomes polarised again and a resting potential is reestablished.
Means an action potential can be generated again
Action potential
Sodium ion channels open
Sodium ions enter cell and cause depolarisation
Sensory neutrons carry
Nerve impulses from receptors towards CNS
Motor neurones carry
Nerve impulses away from the CNS to effectors
Sympathetic nervous system
Stimulates effectors and speeds up any activity.
Controls effectors during strenuous exercise or powerful emotions helping us cope with stressful situations.
Parasympathetic nervous system
Inhibits effectors and slows down any activity.
Controls activity under normal resting conditions.
Conserves energy and replenishes body’s reserves.
Taxes
Simple, directional response
Kinesis
Response which is not directional but instead affects the speed to try and find a new environment
Tropism
Direction of growth in plants affected by different stimuli
IAA
A plant growth factor which inhibits growth in the root and promotes growth in the stem tip
Central nervous system
Made up of brain and spine
Peripheral nervous system
Made up of the nerves that originate in brain if spine and is split into sensory and motor neurones
Rhodopsin
Pigment used in rod cells
Iodopsin
Pigment used in cone cells
Sympathetic nervous system
Stimulates effectors and speeds up an activity
Parasympathetic nervous system
Inhibits efforts and slows down an activity
Sinoatrial node
Group of cells found above the right atrium which stimulates heart contraction
Medulla oblongata
Region of the brain which controls heart rate
Nervous system
Uses nerve cells to pass electrical impulses
Responses are rapid and temporary
Hormonal system
Uses bloodstream to transport hormones to cells
Response is slower and often long-lasting
Neurone
Specialised cell for transporting impulses
Consists of cell body, dendrons, an axon and Schwann cells
Myelin sheath
Portions of lipid-rich membrane that wrap around nerve cells to insulate them and allow faster impulse transmission
Depolarisation
Sodium ions flood into the axon flipping the charges and causing an action potential
Hyper polarisation
As potassiums ions flood out of the axon carrying an unusually high negative charge within the axon
Refractory period
Sodium voltage gates close and it is impossible for another impulse to be passed on
Allows differentiation between impulses
Sarcomere
Portion of myofibril between Z lines and containing the A band and the H zone
Slow-twitch fibres
Contract more slowly and with less force but over a longer period
Large store of myoglobin
Fast twitch fibres
Contract quicker and with more force but over a shorter period of time
Large store of phosphocreatine
Sliding filament mechanism
Theory that actin and myosin fibres slide past each other during contraction
Phosphocreatine
chemical used to rapidly regenerate ATP. Stored in the muscle and is reserve store of phosphate
Homeostasis
Maintenance of an internal environment within strict limits in organisms
Insulin
Hormone produced by beta cells in the islets of the langerhans that convert glucose into glycogen
Glucagon
Hormone produced by alpha cells in the islets of langerhans that convert glycogen into glucose
Negative feedback
Process by which the body responds to a bodily condition staying away from the ideal level.
It brings back to a normal level
Glycogenesis
Conversion of glucose to glycogen
Glycogenolysis
Breakdown of glycogen into glucose
ADH
Hormone produced in the hypothalamus and secreted by the pituitary gland. It affects the permeability of the distal convoluted tubule
Loop of Henley
Section of the nephron that begins in the cortex, drops into the medulla and returns into the cortex. It primarily deals with the reabsorption of water from the filtrate
Glomerulus
Ball do intertwined capillaries that are situated in the bowmans capsule
The filtrate is forced out here
Podocytes
Cells surrounding the glomerular capillaries.
They allow the movement of necessary molecules
Glycogenesis
The conversion of glucose to glycogen in response to high blood glucose concentrations. The liver removes glucose from the blood and converts it to glycogen.
Glycogenolysis
Breakdown of glycogen to glucose in response to low blood glucose concentrations. The liver can convert stored glycogen into glucose which diffuses into the blood.
Gluconeogenesis
Production of glucose from sources other than carbohydrate. When the glycogen supply is exhausted, the liver can produce glucose from non-carbohydrate sources such as glycerol and amino acids
Afferent arteriole
Group of blood vessels that supply the nephrons. Diverge into capillaries of glomerulus
