Unit 1: Module 1 Flashcards
Define Response
It is the change in behaviour or physiology as a result of a change in the environment
Define Stimulus
It is any change in the environment which causes a response
What is needed for a good communication system? State 5 things.
1) Must cover the whole body
2) Must enable cells to communicate
3) Must enable specific communication
4) Must enable rapid communication
5) Must enable ST and LT responses
Cell signalling includes which systems?
The neuronal system and the hormonal system
What are the features of a neuronal system?
- It has interconnected network of neurones
- Signals each other across a synapse junction
- Conduct signals really quickly and responds quickly
What are the features of the hormonal system?
- Uses blood to transport signals
- Cells in endocrine organ release signals (hormones) directly into blood
- Signals are carried all over the body but recognised only by target cells
- Allows LT responses to be coordinated
Define Homeostasis
It is the maintenance of internal environment despite external changes
Define Negative feedback
It is the process that brings about a reversal of any change in condion.
E.g. ^temp = Sweating : Cool down
What must be kept constant for homeostasis? List 6 things.
1) Body temp
2) Blood glucose conc.
3) Blood salt conc.
4) Water potential of blood
5) Blood pressure
6) CO2 Conc.
Define positive feedback
Is the process that ^any change detected by receptors. Tends to be harmful and doesn’t lead to homeostasis.
Provide an example of a Positive feedback mechanism
1) During birth Cervix begins to stretch
2) This signals the pituitary gland
3) This stimulates the secretion of the hormone Oxytocin
4) This increases Uterine contractions
5) This enables Cervix to stretch more which stimulates the secretion of more Oxytocin
6) Then this allows Cervix to dilate more until the baby is born
Oxytocin is also known as the “Tend or befriend” hormone, because it prompts mother to protect her children
Define endotherm
Organisms that can maintain their own body temp. despite of external temperatures
Define Ectotherms
Organisms that rely on external sources of heat to regulate its body temp.
List features of an Ectotherm
- Can generate heat internally by ^ in respiration
- Use less food in respiration
- Can survive long periods without eating e.g. Snakes
- Most of their energy from food is used in growth
- Less active in winter (Predation)
- Must have sufficient energy store to survive through winter
- Can change physiology to ^ absorption of heat from environment e.g. Lizards bask in sun, orientate their body towards or away from sun, shade etc
Why are sensory receptors called energy transducers?
Because they can change one form of energy to another form. For example light energy to electrical (Nerve impulse)
By what receptors are light and colour detected?
Rods and Cones
By what cells are volatile chemicals detected?
Olfactory cells
By what receptors are soluble chemicals detected?
Taste buds
By what receptors are pressure detected on the skin?
Pacinian corpuscles
By what receptor are vibrations in the air detected?
Cochlea
Neurones have specialised channel proteins that are specific to what?
To Na and K
Define a polarise mem. And state how this is achieved.
A polarised mem. is one that has a potential difference across it. This is the (r.p). It is achieved by moving more Na ions out of cell than K ions in. Which causes inside of cell to e more (-ve) charged.
How is a nerve impulse created?
By the opening of Na ion channels to increase permeability across the cell membrane to allow more Na ions to move across down their conc. gradient and into the cell. Thus inside of cell becomes less negative compared to outside
Define depolarisation
This is the period when Na ions entering the cell make inside less negative with respect to outside
Define generator potential
This is a small depolarisation that is caused by the movement of Na ions into the cell
When do more gated channels open?
When there is a greater stimilus. Therefore allows enough Na ions to enter cell, which causes a significant change in (P.d) and initiates an impulse or (a.p)
Define Action Potential
This is achieved when mem. is depolarised to a value of about +40mV. This is known as all or nothing event, events leading up to membrane depolarising and reaching a threshold. Which allows Na ions enter axon and for (a.p) to be reached
What happens in terms of energy when an stimulus is detected?
Energy is converted to depolarise the receptor cell mem. which can then travel around body. The impulse is passed on along neurones as (a.p)
Where do Sensory receptors carry the impulses?
To the CNS
What do the relay neurones do?
They connect the sensory and motor neurones
What do motor neurones do with the impulses?
They carry the (a.p) from CNS to effector (Muscle/ Gland)
List features of a neurone
- Many are very long to transmit (a.p) over a long distance
- Cell surface mem. (Plasma) has many gated ion channels that control entry/exit of (Na, K, Ca) ions
- Have Na/K pumps that use ATP to actively transport Na ions out of cell and K ions in
- Maintain (P.d) across cell surface (plasma) mem.
- Surrounded by fatty sheath (Myelin) which consists of a series of cells called Schwann cells. These insulate neurone from electrical activity in nearby cells.
- There are gaps where Schwann cells meet called Nodes or Ranvier which allows nerve impulses to be conducted quickly by jumping from Node to Node
- Cell body contains Nucleus, many mitochondria and ribosomes
Where is the cell body of a motor neurone located? And why do they have a long axon?
Their cell body is found in the CNS. An have long axon to carry (a.p) out to effector
What do the dendron of a sensory neurone do? And where are the possitioned? Finally why do sensory neurones have short axon?
Long dendron to carry (a.p) from sensory receptor to cell body. Positioned just outside of the CNS. Have short axon to carry (a.p) into CNS
What is a (r.p)?
It is the potential difference or voltage across neurone cell mem. whole neurone at rest. The value is about -60mV inside cell
Define Voltage- gated channels
It is a passage of charged particles/ions. Gates open due to (p.d)
Define Threshold
This is when the (p.d) value across mem. is -50mV. If there is no Threshold then there is no (a.p)
Define Local currents
This is the movement of ions along neurone
Define Neurotransmitter
Are chemicals that diffuse across synaptic cleft of synapse to transmit signal to post- synaptic neurone. An example of a neurotransmitter is acetylCholine
Define Cholinergic Synapses
Are synapses that use acetylCholine as their transmitter substance
Define synaptic Knob
This is a swelling at end of pre-synaptic neurone
Which channels respond to transmitter substance?
Specialised Na ion channels
How do transmissions occur across a synapse?
1) (a.p) arrives at synaptic knob
2) Voltage gated Ca ion channels open
3) Ca ions diffuse into synaptic knob
4) Ca ions cause synaptic vesicles to move and fuse with pre-synaptic mem.
5) Acetylcholine is released (Exocytosis)
6) these diffuse across Synaptic cleft and bind with receptor sites on Na ion channels in post-synaptic mem.
7) Na ion channels open
8) Na ions diffuse across post-synaptic mem. into post-synaptic neurone
9) (G.p) or excitatory post-synaptic potential (EPSP) is created
10) if enough (G.P) combine then (P.d) across post-synaptic mem. reaches Threshold potential
11) New (a.p) is created in Post-synaptic neurone
What does enzyme Acetylcholinesterase do?
Hydrolyses acetylcholine to its products of ethanoic acid + choline
Which then become recycled
Define All or nothing
Neurone either conducts an a.p or not
Define Summation
Several small potential changes combine to form one large change in p.d. across mem.
What are the advantage of myelinated neurones? List 2.
1) a.p. Conducts much more quickly
2) more rapid response to stimulus
Define Hormones
Are chemical messengers released from endocrine glands directly into blood to activate target cells
Define Exocrine glands
Glands that have no ducts and secrete hormones directly onto blood
Define Exocrine gland
Gland that has ducts and secretes molecules to be carried to where it is needed
Define First messenger
Are hormones that transmit signals around the body
Define secondary messenger
cAMP that transmits signals inside cell
Define Pancreatic duct
This is the tube that collects secretion from exocrine cells and carries fluid to small Intestine
Define Insulin
Hormone that causes blood glucose levels to decrease
Define Glucagon
It is a hormone that causes blood glucose levels to increase. (Opposite to Insulin)
What is the normal conc. of glucose in blood?
90mg 100cm^-3
What cells detect high conc. of blood glucose?
B - Cells
Which cell detects low conc. of blood glucose?
a - cells
Define Diabetes mellitus
This is a disease where blood glucose conc. cannot be controlled effectively
Define Hyperglycaemia
This is a state where blood glucose conc. is too high
What defines Genetically engineered bacteria?
The fact that their DNA has been altered
Define stem cells
Are unspecialised cells that have the potential to develop into any type of cell
Define cell metabolism
This is the result of all the chemical reactions taking place in the cytoplasm
Define Myogenic
Is the muscle tissue of the heart that can initiate its own contractions
Define pacemakers
Is region of tissue in the R.atrium wall = generate impulse and initiate contractions of chambers in heart
Define medulla oblongata
This is found at base of brain. Coordinates unconscious functions e.g. Breathing rate, heart rate
