week 3 Flashcards
Body defences, nervous system structure + function
Antigen
capable of introducing an immune response
anything foreign to the host
Body defences (list 2)
non-specific
specific
Non-specific defences
general defence/ attack on all antigens
first and second line defences
react the same each time
Specific defences
specialist/ targeted defence against one type of antigen
third line defences
First line defences
keep invaders out via chemical and physical barriers
skin - epidermis, sebum + sweat
mucous membranes - mucous, hairs + cillia
fluids - tears, saliva, nasal secretions + urine
defecation - vomiting, coughing + sneezing
Second line defences
act once microbes have entered the body
antimicrobial chemicals phagocytes natural killer cells inflammation fever
Antimicrobial chemicals
is an agent that kills microorganisms or stops their growth
Phagocytes
attracted to the affected site by chemotaxis, destroy bugs and clean up dead tissues
Natural killer cells
immune surveillance- targets abnormal cells
Inflammation
the bodies response to damages cells, destroys and removes antigens, cleans up dead tissue + debris
Fever
systemic response
temp increases to kill of bugs
higher metabolic rate
Third line defences
develops on exposure to a particular antigen
uses B + T lymphocytes made in bone marrow
B and T cells (where they mature + type of immunity)
B cells -> mature in bone marrow
T cells -> mature in thymus
T cells are involved in cell-mediated immunity
B cells are primarily responsible for humoral immunity
Functions of the nervous system (3 components)
sensory - knows whats happening
integrative - makes decisions
motor - does something about it
Two parts of the nervous system
central nervous system (CNS)
- brain + spinal cord
peripheral nervous system (PNS)
- all nervous tissue outside the CNS
PNS divisions (2 parts)
afferent (sensory information)
efferent (motor commands)
Afferent (sensory)
brings sensory information to the CNS from the receptors situated in peripheral tissues + organs
Efferent (motor) 2 sub categories
somatic nervous system (SNS)
- controls skeletal muscle movement
- involuntary + voluntary
autonomic nervous system (ANS)
- parasympathetic (rest and digest) + sympathetic (fight or flight)
- controls subconscious actionsNeural tissue (2 parts)
neurons - cells that send + receive signals
neuroglia (glial cells) - cells that support + protect neurons
Neurons and synapse elements (cell body, dendrite, axon, axon terminal, synapse)
cell body
- nucleus
- organelles
dendrites
- highly branches
- receive input from other neurons and take it to cell body
axon
- single long process
carries electrical signals (action potential) away from cell body to other neurons or effectors
axon terminals
- some enlarge -> synaptic end bulbs
- synaptic vesicles release neurotransmitters
synapes
- structure that allows a neuron to communicate with another cell
- pre-synaptic: neuron that sends message
- post-synaptic: neuron that receives message
- synaptic cleft: the small gap that separates the pre-
synaptic and post-synaptic membrane
Neurotransmitters
a chemical substance which is released at the end of a nerve fibre by the arrival of a nerve impulse and, by diffusing across the synapse or junction, effects the transfer of the impulse to another nerve fibre, a muscle fibre, or some other structure.
Nerve fibres
the axon of a neuron
axons run together
- CNS: tract
- PNS: nerve
Neuronal cell clumps (in the CNS + PNS)
CNS -> nucleus
PNS -> ganglion
Myelin sheath
made by glial cells
fatty white sheath around axons
increase speed of transmission
White + grey matter
white matter - myelinated nerve fibres
grey matter - un-myelinated cell bodies and dendrites
Resting membrane potential
ECF + ICF differ in ionic composition
- high concentration of K+ inside - high concentration of Na+ outside
Na+/K+ Exchanger
- Active transport
- uses ATP
- Transports
- 2 K+ into the cell
- 3 Na+ out of the cell
Action potential
the membrane gets less negative and then returns to the resting level -> action potential
- depolarisation (inside cell becomes less negative)
- for a short time the cell becomes (+) - repolarisation (inside of the cell is becoming more negative)
- hyperpolarisation (it becomes more negative than at rest)
- resting membrane potential
Depolarisation
Na+ ions enter the cell through voltage-gate Na+ channels and make the cell become less negative
Repolarisation
K+ ions leave the cell through voltage-gated K+ channels and the cell becomes more negative
Hyperpolarisation
too many K+ ions leave the cell and cell become more negative than at rest
Refractory periods
absolute refractory period - no new action potential can be evoked
relative refractory period - new action potential can be evokes (requires a very strong stimulus)
Synapes/ neurotransmission process
- action potential travels along axon and reaches the pre-synpatic terminal
- Ca+ channels open
- Ca+ enters
- neurotransmission chemical (acetylcholine)
- Ca+ and the neurotransmission chemical form balls
- Neurotransmission chemicals diffuses across the synaptic cleft
- the neurotransmission chemical binds to the receptor (ion channels)
- ion channels open
- cations such as sodium flow into the post-synapetic terminal
- if the sodium generates a big enough depolarisation the action potential continues along the next axon
Label the neuron
cell body nucleus dendrites axon terminal axon action potential
