13 Flashcards
what 2 ways do animals communicate
*chemical - using hormones
electrical - using neurones
internal changes?
*Water potential
*Cell pH
*Glucose level
*Internal temp
external changes
*Light
*External temp
*New or sudden sound
*Humidity
why is coordination important?
organisms evolve and therefore certain cells may become specialised. The organism will need to coordinate these cells and systems to operate effectively.
coordination example
RBC carries O2 but relies on stem cells for RBC reproduction as RBCs dont have nucleus. However, stem cells are unable to respire and produce RBCs w/o O2. Therefore RBCs and stem cells work in coordination.
Homeostasis
The maintenance of relatively constant conditions in the body.
homeostasis p2
communication and coordination allows us to maintain homeostasis
cell signalling
*Neurotransmitters between neurones signal locally
*Hormones transfer signals across larger areas
plants signalling
use hormones to respond to stimuli e.g growth toward light
Neurones?
specialised cells that transmit electrical receptors
synapse?
The gap between 2 nerve cells in which neurotransmitters are used to transfer the signal
Reflex arc (refresher)
1 - stimulus
2 - receptor
3 - sensory neurone
4 - synapse
5 - relay neurone
6 - synapse
7 - motor neurone
8 - effector
what do nerve cells do?
transmit impulses from relay or sensory neurones to effectors such as muscles or glands
Sensory neurone
Transmits signals from sensory neurone to relay neurones, motor neurones and Brain
Relay neurone
Transfer impulses between neurones
*also called interneuron
Shwan cells
Produce layers of plasma membrane around the axon of some neurons
myelinated neurones
conduct impulses much faster compared to unmyelinated.
nodes of Ranvier -
gaps between myelin sheath
*allows node impulses to jump from one node to the next
Central nervous system
Brain and spinal chord
Peripheral nervous system
Everything else not in CNS
Autonomic nervous system (under peripheral)
controls unconscious/ involuntary processes e.g heartbeat
Somatic nervous system (under peripheral)
plays the role in voluntary movements
sympathetic (under somatic)
Responsible for fight or flight e.g higher heart rate, more alert
parasympathetic (under somatic)
responsible for rest and digest e.g lower heart rate and increased rates of digestion
What are internal factors that an organism may respond to?
Blood glucose
Internal temp
Water potential
Cell pH
What are some external factors that an organism may respond to?
Humidity
External temp
Light intensity
New or sudden sound
Describe the cell body of a neurone?
Contains nucleus surrounded by cytoplasm.
Many ER and mitochondria in cytoplasm used to produce neurotransmitters.
What are dendrons?
Short extensions which come from cell body. The extensions divide into smaller branches called dendrites.
Transmit electrical impulses towards cell body.
What are axons?
Singular elongated nerve fibres.
Transmit impulses Away from cell body.
Cylindrical fibre with very narrow region of cytoplasm surrounded by plasma membrane.
What are the different types of neurones?
Sensory, relay, motor.
What do sensory neurones do? And do they have an abundance of axons and dendrons or not?
Transmit impulses from sensory receptor cell to relay neurone, motor neurone or brain.
They have one dendron.
Have one axon.
What do relay neurones do? And do they have an abundance of axons and dendrons or not?
Transmit impulses between neurones.
Have many short axons and dendrons.
What do motor neurones do? And do they have an abundance of axons and dendrons or not?
Transmit impulses from a relay neurones or sensory neurone to an effector.
Have one long axon and many short dendrites.
What does the nervous response pathway look like?
Receptor -> sensory neurone -> relay neurone -> motor neurone -> effector cell
Whats a transducer?
Something that changes one form of energy into another
Where is cell body in motor neurone?
At end of cell
What is the myelin sheath made of?
Schwann cells
What does myelin sheath do?
Acts as insulating layer and allows neurones to conduct electrical impulses at much faster rate.
What is a node of ranvier?
Small gap between each adjacent schwann cell.
Electrical impulses jump from one node of ranvier to the next as it travels along the neurone.
Why do electrical impulses need nodes of ranvier to move along a myelinated neurone?
As the myelin sheath is wraped so tightly around the neurone that it prevents the movement of ions across the neurone membranes and so the the action potential has to jump from one node to the next
Can non myelinated neurones have schwann cells?
Yes but several neurones will be enshrouded by a loosely wrapped schwann cell.
What are the two main features of sensory receptors?
- specific to a single type of stimulus
- act as a transducer - they convert stimulus into a nerve impulse
Whats an effector?
An organ that becomes active in response to a nerve impulse
What are the 4 main sensory receptors in animals?
-mechanoreceptor - pressure and movement - pacinian corpuscle - skin
-chemoreceptor - chemicals - olfactory receptor - nose
-thermoreceptor - heat - end bulbs of Krause - tongue
-photoreceptors - light - cone cell - eye
What is a pacinian corpuscle?
Specific sensory receptor that detects mechanical pressure
Where is pacinian corpuscle found?
Deep within skin and mainly around fingers and soles of feet
How does pacinian corpuscle convert mechanical pressure to nervous impulse?
1) in resting state, the stretch-mediated sodium ion channels in sensory neurones membranes are too narrow to allow sodium ions to pass through them. This is resting potential.
2) when pressure is applied to pacinian corpuscle, it changes shape. This causes the membrane surrounding its neurone to stretch.
3) when the membrane stretches, thee sodium ion channels present widen. Sodium ions can now diffuse into neurone.
4) the influx of positive sodium ions changes the potential of the membrane - it becomes depolarised, resulting in generator potential.
5) in turn the generator potential creates action potential that passes along sensory neurone.
The action potential will then be transmitted along neurones to CNS.
