Module 5.1.1 - Neuronal communication Flashcards
What is homeostasis?
Maintenance of relatively constant conditions inside the body
What are some external changes to the environment?
- temp
- soil pH
- light intensity
- loud noises
What are some internal changes to the environment?
- pH in blood
- blood glucose
- temp
- water potential
Do plants have a nervous system?
No but can still respond to changes in environment to survive
How to animals react to change?
Electrical responses via neurones and chemical responses via hormones
How do plants react to change?
Chemical responses via hormones
What is the nervous system?
Electrical impulses that detect changes/stimuli
What is a motor neurone?
Transmits impulses from relay or sensory neurones to an effector
What is a relay neurone?
Transmits impulses between neurones
What are parts of a relay neurone?
Cell body, dendrons, axons, nucleus, dendrites
What are parts of a motor neurone?
Cell body, dendrites, cytoplasm, nucleus, myelin sheath, axon, node of Ranvier, axon terminals
What is a sensory neurone?
Neurone that transmits impulses from receptor cell to relay or motor neurone or brain
What are parts of a sensory neurone?
Dendrites, dendron, myelin sheath, nucleus, cytoplasm, neurotransmitters, cell body, axon, node of Ranvier, axon terminal
What is the process from stimuli to response?
Stimuli, receptor, sensory neurone, relay neurone, motor neurone, effector, response
What are Schwann cells?
Produce large layers of plasma membrane around an axon, called myelin sheath
- type of glia cells
What is saltatory conduction?
Impulse jumping from each node of Ranvier (small gap in between each myelin sheath) to the next
What is multiple sclerosis?
Impaired Schwann cells, brain detects myelin as foreign so breaks it down, own immune system damages you
- results in loss of muscle control, vision and balance
What are sensory receptors?
Allow body to detect changes in environment, often located in sense organs, specific to 1 type of stimulus
What do sensory receptors act as?
Transducers
What are transducers?
Sensory receptors convert stimulus into nerve impulses called generated potential, this is then passed through nervous system to brin a response by sending out impulse to an effector - action potential
What are Pacinian corpuscle?
Specific sensory receptors that detect mechanical pressure
- located deep within the skin, most abundant in fingers and soles of feet
How does depolarization in Pacinian corpuscles happen?
Pressure is applied/ stimulated which widens the stretch median sodium channels, allowing sodium ions to enter which makes the cell positive
- generated potential is created
- a nerve impulse/action potential is then generated
What is resting potential?
Outside of membrane is more positive than outside, is polarized, around -70mV
What is action potential?
Stimulus detected by sensory receptor, energy of stimulus temporarily reverses charge on axon membrane, potential difference across membrane is +40mV, depolarized, when impulse passes is repolarizes neurone back to resting potential
What is the refractory period?
After action potential, short period of time when axon cannot be excited again, voltage gated sodium ion channels remain closed
Why is the refractory period importnat?
Make sure action potential travels in 1 direction and they don’t overlap
How can action potential be sped up?
- myelination
- axon diameter, less resistance to flow of ions in cytoplasm if large axon diameter
- temperature, diffuse faster at high temp but will denature if too high
What is the all or nothing principle?
Nerve impulses said to be all-or-nothing response, threshold value must be reached to trigger a response, no matter the stimulus the same sized action potential will be triggered
What is a synapse?
Junction between 2 neurones or a neurone and effector
What do synapses do?
- ensure impulse is unidirectional
- impulse from 1 neurone to be transmitted to many
- impulses from many neurones to be transmitted to 1
How do synapses work?
- action potential causes voltage gated calcium channels to open, influx calcium ions down electrochem gradient
- vesicles fuse with pre synaptic membrane, voltage gated sodium channels on post synaptic membrane
- neurotransmitters bind to receptors on v-g Na+ channels and they open
- influx Na+ ions down electrochem gradient, +ve charge causes depolarisation , generate action potential
What is ACH and ACHE?
ACH - acetylcholine is a neurotransmitter
ACHE - acetylcholinesterase is an enzyme that breaks down ACH that’s binded to receptors
What does ACHE do?
- breaks down ACH into choline and acetyl that diffuse down conc gradient into pre sysnaptic neurone
- ATP energy creates bonds between choline and acetyl to create ACH
- it is repackaged in ER as a vesicle
What are the 2 types of neurotransmitters?
- excitatory
- inhibitory
What is the neurotransmitter excitatory?
Results in depolarisation of post synaptic neurone. If threshold reached in post synaptic membrane, action potential is triggered.
e.g. ACL
What is the neurotransmitter inhibitory?
Results in hyperpolarisation of post synaptic membrane. Prevents action potential from being triggered
e.g. Gamma aminobutyric acid
What are the 2 types of summation?
- temporal
- spatial
What is temporal simmantion?
Constant firing of neurotransmitters from 1 pre synaptic neurone
What is spatial summation?
Multiple pre synaptic neurones working together to reach threshold for action potential
What are the top 2 parts of the nervous system?
Central nervous system
Peripheral nervous system
What 2 nervous systems come from the peripheral nervous system?
Somatic NS
Autonomic NS
What is in the CNS?
- brain
- spinal chord
- relay neurone
What is in the peripheral NS?
- nerves around the body
- sensory and motor neurone
- Pacinian corpuscle
What is the somatic NS?
Conscious control
- speech
- movement
What is the autonomic NS?
Subconscious control
- breathing
- blinking
- swallowing
- heartbeat
- digestion
- vomiting
What 2 nervous systems come from the autonomic NS?
Sympathetic NS
Parasympathetic NS
What is the sympathetic NS?
Fight or flight response
- uses noradrenaline (NA)
What is the parasympathetic NS?
Relaxing response
- uses Acetylcholine (ACH)
What are the parts of the brain?
- cerebrum
- cerebellum
- medulla oblongata
- pituitary gland
- hypothalamus
What us the cerebrum?
- voluntary actions
- highly folded to increases SA and capacity for complex activity
- split into 2 hemispheres, each receive impulses from opposite sides of body
Whatv are the lobes of the cerebrum and what do they do?
Frontal lobe - motor function, problem solving, memory, language, judgement, behaviour, personality
Parietal lobe - integrating sensory info, taste, smell
Temporal lobe - listening, general speech perception, communication
Occipital lobe - visual processing
What is the cerebellum?
- controls muscular movement, posture and balance
- doesn’t initiate movement but just coordinates it
- receives info from ears about balance and tone of muscles and tendons from the body
What is the medulla oblongata?
- controls reflex activities such as heart rate, breathing rate
- important in autonomic nervous system, controlling swallowing, coughing, sleep and peristalsis
What is the hypothalamus?
- controls hormones and homeostasis
- controls pituitary gland, temperature and blood pressure
What is the pituitary gland?
- anterior pituitary (front) secretes hormones and produces them
- posterior pituitary (back) stores hormones and releases them to hypothalamus
What is a reflex action?
Involuntary response to a sensory stimulus
Why are reflexes important for survival?
- avoid harm of body or reduce severity of harm
- leaves brain to deal with more complex responses because they’re involuntary, prevent brain overload
- present at birth, don’t have to be learnt, provide immediate protection
- reflex arc is short and fast
- many are every day actions
What is the reflex arc pathway?
- receptor detects stimulus and creates action potential
- sensory neurone carries impulse to spinal chord
- relay neurone connects sensory and motor neurone
- motor neurone carries impulse to effector
- response is carried out
What is a knee-jerk reflex?
- spinal reflex, from spinal chord not brain
- commonly used by doctors
What is the blinking reflex?
- cranial reflex so only occurs in brain not spinal chord
- both eyes will blink when cornea is stimulated
What muscle causes the eye to blink?
Orbicularis oculi
What is the blinking reflex pathway?
- stimulus in cornea triggers an impulse
- impulse sent along sensory neurone
- passes through relay neurone in lower brain stem
- sent along branches of motor neurones
- response is triggered of closing eyes
What are the 3 types of muscles and are they voluntary or involuntary??
cardiac - involuntary
skeletal - voluntary
smooth - involuntary
What is a muscle fibre?
cell
What is the sarcomere?
- functional region of myofibrils, it contracts when a muscle contracts
- contains actin, myosin, light band, dark band, H zone, Z line,
What contained in the skeletal muscle?
- lots of mitochondria to provide ATP for muscle contractions
- sarcolemma which is the specialised plasma membrane for muscle cells
- sarcoplasm reticulum contains calcium ions needed for muscle contractions
- striated/stripey myofibrils
- t tubules, extensions of sarcolemma, help spread electrical impulses through sarcoplasm
- sarcoplasm is the shared cytoplasm within a muscle fibre
What are myofibrils?
- long cylindrical organelle, made up of protein, specialised for contraction
- myosin is a thicker filament, long tod shaped fibred with bulbous heads that project to 1 side
- actin is a thinner filament, 2 strands twisted around each other
What are parts of the sarcomere?
- Z line will move closer together with contractions
- light band contains actin only
- dark band contains actin and myosin
- H zone contains only myosin which narrows with contractions
What are the 2 types of twitch fibres?
Slow and fast
What is the cardiac muscle?
- found only in heart, myogenic so heart beats regularly
- specialised striated
- involuntary
- intermediate contraction speed’- intermediate contraction length
What is the skeletal muscle?
- makes up bulk of body muscle tissue and is responsible for movement
-straited - voluntary
- rapid contraction speed
- short contraction length
What is the smooth muscle?
- found in many parts of body, e.g. walls of hollow organs like stomach and blood vessels
- non straited
- involuntary
- slow contraction speed
- can remain contracted for a very long time
What is the sliding filament model?
Where actin and myosin filaments slide past each other to contract and cause movement
What is tropomyosin?
- covers binding sites on actin in resting state
- held in place by troponin (protein)
How does the sliding filament model work?
- (stimulation) - tropomyosin covers binding site
- held in place by troponin
- ADP attached to myosin bulbous heads - action potential arrives
- depolarisation of sarcoplasmic reticulum + sarcolemma
- voltage gated Ca2+ channels open
- action potential arrives
- Ca2+ diffuses through sarcoplasm
- binds to troponin
- conformational change, exposes binding sites on actin
- Ca2+ diffuses through sarcoplasm
- (attachment) - myosin head binds to actinmyosin binding site
- forming cross bridges - myosin head flexes to pull actin alonh
- releases ADP
- myosin head flexes to pull actin alonh
- (detachment) - ATP binds to myosin head
- detaches from actin - Ca2+ activates ATPase on myosin head
- hydrolyses ATP to ADP + Pi
- energy released returns myosin head to original position
- Ca2+ activates ATPase on myosin head
What are the 3 stages of the sliding filament model?
- stimulation
- attachment
- detachment
