Week 5: Nervous System Flashcards
The 2 basic cell types of nervous tissue
Neurons (electrical conduits)
- sensory
- motor
- inter-neurons
Glial cells (supporting cells)
- Phagocytes (immune cells)
- insulation (myelin)
- support and protect neurons
- produce growth factors
- Do not transfer information
What does amitotic mean
The can’t divide or repair
The 4 components of the synapse
- Synaptic vesicles (containing neurotransmitter)
- pre-synaptic neuron
- synaptic cleft
- post-synaptic membrane`
What are the 2 biogenic amines: potent neurotransmitters
Catcholamines
-Norepinephrine, Dopamine
Indolamines
-Seratonin
(More info on slides (chemical synapses and neurotransmitters)
Difference between chemical and voltage gated channels
Chemical:
-Open in response to binding of appropriate neurotransmitter
Voltage:
-Open in response to changes in membrane potential
What is Depolarisation and Hyperpolarisation relative to the Resting membrane potential
- depolarization = membrane potential becomes less
negative than -70mV (up to +30mV) - hyperpolarization = membrane potential becomes more
negative than -70mV
Two types of signals
- Graded potential: short distance
- Action potential: long distance signals of axons
Generating the action potential
An action potential is a brief reversal of membrane
potential (in nerves also called a ‘nerve impulse’
• Resting state: All gated Na+ and K+ are closed.
• Depolarisation: Na+ channels open, at threshold becomes self generating
– Positive feedback
• Repolarisation: Na+ are inactivating, K+ channels open
• Hyperpolarisation: Some K+ remain open, Na+ channels reset.
The action potential
• Stimulus must initially reach a “trigger” potential (- 55mV).
• Large change in membrane potential then spreads down entire length of
axon (all or nothing “domino” effect).
• Magnitude is sustained with time and distance.
Structural region of the brain
- Ventricles
- Cerebrum
- Diencephalon
- Brain stem
- Cerebellum
Structure of the cerebrum
- Largest brain component (83%)
- Cerebral cortex
- Cerebral white matter
- Basal nuclei
Functions of the cerebral cortex
Consciousness voluntary movement communication understanding intelligence/reasoning/logical thought memory personality morals, beliefs, values social behaviour
Cerebral cortex - functional domains
- Comprised of gray matter
- 2-4mm thick containing billions of nerve cells arranged in 6 layers
- 40% of total brain mass
- all neurons in the cortex are interneurons
3 functional domains
- motor
- sensory
- associated
Sensory cortex function
- Somatory (skin, proprioceptors, feeling)
- visual
- auditory
- vestibular (balance)
- olfactory (smell)
- Gustatory (taste)
- Visceral (sensations)
Multimodal association areas function
Anterior association area (prefrontal cortex)
- Working memory (comprehension of abstract ideas, judgement, reasoning, persistence, planning)
- Maturation dependent on social environment feedback
Posterior association area
- Combines temporal, parietal and occipital lobes
- pattern and face recognition
- spatial awareness
- combining sensory inputs
- comprehension of written and spoken language
Limbic association area
- Emotional impact
- Memories
lateralisation of cortical functioning
Lateralisation
- We use both hemispheres for most activities
- But there is a division of labour
Cerebral dominance (language) - One cerebral hemisphere will dominate in each task
Most individuals with left cerebral dominance are right handed.
What three different fibres is cerebral white matter composed of
Commissural fibres
Association fibres
Projection fibres
3 paired structures of Diencephalon
Thalamus
Hypothalamus
epithalamus
Thalamus function
Makes up 80% of the diencephalon
Relay station into the cerebral cortex
Hypothalamus function
Most important section Control centre of the body (homeostasis) -Autonomic nervous system -Physical responses to emotion -Body temperature regulation -Food intake regulation -Water balance and thirst -sleep-wake cycles -endocrine system control
epithalamus function
Dorsal portion of diencephalon
contains the pineal gland
-secretes melatonin hormone
-controls sleep-wake cycles
Brain stem function
Produces the rigidly programmed, automatic behaviours necessary for survival Has 3 sections -Midbrain (top of stem) - Pons (bridge) -Medulla oblongata
Midbrain and pons function
Midbrain Houses cerebral aqueduct involved in pain suppression linked to 'fight-or-flight' response substantia nigra releases dopamine red nuclei: descending motor pathway causing limb flexion
Pons
chiefly composed of conduction tracks
Medulla oblongata
Blends into the spinal cord at its base
Contains the decussation of the pyramids
Function
autonomic reflex centre involved in maintaining homeostasis
-Cardiovascular - heartbeat, blood pressure
-Respiratory system - Breathing
-other responses such as hiccups and vomitting
Cerebellum processing
voluntary muscle contractions proprioceptions co-ordination autopilot cognition (thinking, language, emotion)
Limbic system
Medial aspect of each cerebral hemisphere and diencephalon
Emotion
Major structures of limbic system
Amygdala
-response to threats
Hippocampus - memory centre
- consolidation of short-term to long-term memories
- spatial memory
Protective mechanisms of the brain
Bone
Meninges
Cerebrospinal fluid
blood brain barrier
Meninges detail
three connective tissue membranes -external to interal are the: Dura mater Arachnoid mater Pia Mater
Blood brain Barrier (BBB) Detail
- BBB maintains the brain’s stable environment.
- Due to capillaries in the brain having exceptionally impermeable tight junctions between the capillary endothelial cells.
more detail on slide)
3 main points PNS includes (Peripheral nervous system)
Sensory receptors
Peripheral nerves
efferent motor endings
PNS sensory receptors: 4 stimulas types
Mechanoreceptors Thermoreceptors photoreceptors chemoreceptors nocireceptors (pain)
PNS Sensory receptors location
Exteroceptors - touch pressure pain temperature interoceptors - Chemical changes proprioceptors - skeletal muscles, tendons, joints, ligaments and connective tissue covering bone and muscle
Peripheral nerve structure 3 layers
endoneurium - delicate layer of loose connective tissue Perineurium - coarser connective tissue wrapping epineurium - tough fibrous sheath
The autonomic nervous system maintains homeostasis by which two opposing branches
sympathetic branch (voluntary control, fight or flight) parasympathetic branch (involuntary control)
