Section 1- Communication And Homeostasis Flashcards
Define Cell Signalling
Communication between cells
Give two examples of Cell Signalling
Neuronal- transport action potentials through neurones and across synapses
Hormonal- transport signals via the blood
Define Negative Feedback
A process which any change in a parameter brings about the reversal of the change, so the parameter remains constant
Define Positive Feedback
A process in which any change in a parameter brings about an increase in that change
Define Homeostasis
The maintenance of a constant internal environment
Explain the Principle Of Homeostasis
Any change is detected by receptors, the communication system transmits a message from the receptor to the effector and, through negative feedback, the effectors revers the change
How do ectotherms maintain a constant core body temperature, physiologically and behaviourally (include examples)
Physiologically - Horned lizard expands its ribcage and the frilled lizard uses its frill to expand its surface area to absorb more heat
Behaviourally - Snakes expose their body to the sun so more heat is absorbed.
Locusts orientate their body towards the sun to expose a larger surface area so more heat is absorbed
Why do we need communication systems in multicellular organisms ?
Organisms need to respond to external stimuli (e.g temperature)
Coordinate different organs
How do endotherms maintain a core body temperature, physiologically
Sweat Glands - secrete sweat when hot, water evaporates using heat from the blood removing this excess heat
Lungs/nose/mouth - when hot pant to increase water evaporation from the lungs, tongue and moist surfaces
Hairs On Skin - hairs lie flat when hot providing little insulation, heat can be lost by convection
Define stimulus
Any change in internal and external environment
Why do organism need to respond to stimuli
To increase their chances of survival
What is the role of a receptor
To detect stimuli
Give two types of cell that can act as effectors
Muscle cells
Cells in glands
What is the function of a sensory neurone
To transmit nerve impulses from receptors to the central nervous system (CNS)
What is the function of a motor neurone
To transmit nerve impulses from CNS to effectors
Give three structural differences between a sensory neurone and a motor neurone
- Dendrites in sensory neurone are further away from the cell body than they are in the motor neurone
- Axon in the sensory neurone are shorter than they are in the motor neurone
- Sensory neurones have dendrons, motor neurones do not
Describe the pathway of nervous communication from stimulus to response
Receptor cell detects stimuli
Sensory neurones transmit electrical impulses from receptors to CNS
CNS processes information and sends impulses along motor neurone to effector
Why are sensory receptors described as a transducers
Convert energy of stimulus into electrical energy
How is a generator potential produced
Stimulus detected
Cell membrane excited
More permeable (more ions to move)
Alter potential across cell membrane
Which two proteins in a neurone’s cell membrane are responsible for creating and maintaining resting membrane potential
Sodium- Potassium pumps
Potassium ion channels
Give three types of cell that have receptors for neurotransmitters
- Neurone
- Muscle
- Gland
Explain how waves of depolarisation are produced
During an action potential
- some sodium ions that enter neurone diffuse sideways
- sodium ion channels in next region open
- sodium ions diffuse into that part
- causes wave of depolarisation
How does the conduction along the myelinated neurone differ compared to conduction along the non-myelinated neurone
- in myelinated neurone the action potentials happen in the node of ranvier
- non-myelinated neurone action potential happens in whole length of axon
- conduction in myelinated happens quicker
Describe the structure of a myelinated neurone
- myelin sheath: made up of Schwann cell wrapped around axon
- between Schwann cells tiny patches called nodes of Ranvier
- sodium ions concentrated at NoR
