Lecture 6: Nervous System Flashcards
What is the stimulus response?
Sensory input –> Integration –> Motor output
Input: millions of sensory receptors that monitor the changes (or stimuli) inside and outside the body
Integration: Processes and interprets the sensory input and decides what to do at each moment (brain and spinal cord)
Output: Effectors or causes a response by activating muscles or glands (effectors) via motor output
What are the functional classification of the PNS?
Sensory/afferent:
-Somatic fibres (muscles)
-Visceral fibres (gut, lungs)
Motor/efferent:
-Somatic nervous system (voluntary)
-Autonomic nervous system (involuntary)
-Sympathetic NS
-Parasympathetic NS
What are the 2 types of principal cells?
- Supporting cells/neuroglia/glial cells
CNS glia:
-Astrocytes
-microglia
-Ependymal cells
-oligodendrocytes
PNS glia:
-Schwann cells
-Satellite cells - Nerve cells/neurons
What is the direction of the fibers/processes in a neuron?
Dendrites: electrical signals towards the cell body, up to hundred depending on the neuron
Axon: electrical signals away from the cell body down the axon, each heron only has 1 axon
Cell body: collections of cell bodies called ganglia
Axon terminal: each one is separated from the next neuron by a gap: synaptic cleft and the functional junction is the synapse
Define the following terms:
Nuclei
Ganglia
Tracts
Nerves
White matter
Gray matter
Nuclei: cluster of neuron cell bodies in the CNS
Ganglia:Cluster of neuron cell bodies in the PNS
Tracts: Bundles of nerve fibres running through the CNS (spinal tract)
Nerves:Bundles of nerve fibers running though the PNS
White matter:Dense collections of myelinated fibres
Gray matter:Mostly unmyelinated fibres and cell bodies
What do interneurons or association neurones do?
-Connect the motor and sensory neurons (cell bodies in the CNS)
What is somatosensory info?
-Neuron with free endings (pain, temp)
-Neuron with encapsulated endings (pressure and touch)
Other than vision, hearing, balance, taste and smell
-Specialized receptor (photoreceptor)
What are the 2 major functional properties of the NS?
Respond: to stimulus (from outside, pressure, heat) and convert it into nerve impulse
Transmit: the impulse to other neurons muscles or glands (motor neurons)
What are the electrical conditions of an inactive neuron?
-Plamsa membrane of an inactive (resting) neuron is polarized = fewer + ions sitting on the inner surface than on the outer surface (more - on inside)
-Major + ions outside the cell: Na+
-Major + ions are on the inside: K+
-As long as the inside remains more - then the outside, the neuron will stay inactive
What is the process of a stimulus initiating local depolarization?
EX. pressure stimuli excites a cutaneous receptor of the skin
-Permeability of the cell plasma membrane changes
-Na+ much higher conc. outside cell and defuses quickly into neuron this is called local depolarization
-Stimulus is strong enough Na+ influx is big enough
-Local depolarization initiates and transmits a long distance signal called AP=nerve impulse
-All-or-none response=conducted over the entire length of the neuron, or it doesn’t happen at all
-Then membrane becomes impermeable to Na+ and permeable to K+
-K+ ions diffuse out of the neuron (repolarized)
-Outflow of + ions restores the electrical conditions to the resting (polarized) ccondition
-After repolarization the initial conc. of Na+ and K+ ions inside and outside of the neuron are restored by activation of the Na+/K+ pump
-Pump uses ATP cellular energy to pump excess Na+ ions out and brig K+ ions in
What happens at a synapse?
-Neurotransmitter chemical crosses gap to transmit signal between neurons
-Neurotrans. binds to a receptor on the next heron and Na+ entry etc occurs
-Most herons communicate via chemical types of synapses, some physically joined by gap junctions
Process
-AP reaches axon and electrical change open Na+ channels
-Vesicles containing neurotrans. fuse with the axon membrane and release the transmitter
-neurotans. diffuses across the synapse to bind to receptors on the next neuron and then the series of events described before will happen reach depolarization
How is a neurotransmitter removed from the synapse?
-By diffusion away
-Reuptake into axon terminal
-Enzymatic breakdown=ion channel closes
What are neurotransmitters and what are some classes of neurotransmitters?
-Chemicals that are used to relay, amplify and modulate signals b/w neurons
-Amino acids
-Monoamines
-Acetycholine (most common) crosses neuromuscular junction and excites muscle cell membrane causing depolarization. and contraction of the muscle fibre, if ACh is not released=muscles can’t contract
-Cholinesterase (enzyme) breaks down Ash so fibre can repolarize or would have constant contractions
What are reflexes?
-Rapid, predicable, involuntary response
-Reflex arcs (neural pathways) involve both the CNS and PNS
-Somatic reflex: fulling finger away from hot plate skeletal muscles activated
-Autonomic reflex: bright light and size of pupils change (regulate body functions of smooth muscles glands and heart)
What are the minimum 5 elements a reflex arc has to have?
- Sensory recpetor
- Effector organ (muscle, gland)
- Sensory neuron
- Motor neuron
- Integration center: spinal cord and or interneurons b/w the sensory and motor neuron
-Note done need brain but need spinal cord
