Week 7 intro to nervous system organisation Flashcards
The nervous system (NS)
Made up of different functional nervous systems
-Electrical and chemical messaging throughout the body
Central nervous system (CNS)
Brain and spinal cord, linked to; peripheral nervous system
Peripheral nervous system
Afferent Nerves: Sensory neurons (messages from periphery to spinal cord)
Efferent Nerves (messages from spinal cord to muscles/glands
-Divided into somatic and
autonomic
Peripheral nervous system
Two key elements, sensing and responding, sensory division (afferent) and motor division (efferent)
Autonomic nervous system
Involuntary control (nervous system), can be divided into two sub units : sympathetic division and parasympathetic division
Functional divisions of the nervous system
Sensory division (sensing) -> CNS -> Motor division (responding) -> somatic nervous system / autonomic nervous system -> (from autonomic nervous system) -> sympathetic division / parasympathetic division
Afferent
Means : towards something
Two key cell types
-Neurons
-Glial cells
Neurons
Responsible for communication
(action potential / neurotransmission)
Glial cells
-Neuroglia or glia
-Supporting cells
Neurons (individual nerve cells)
Specialised cells:
-Transmit information as electrical signals - nerve impulses or action potentials (AP)
Neurons structure
Main part: cell body/soma
Extensions of cell membrane
-Single axon: divides to
communicate with other cells
-Dendrites: receives info from
other cells
-Connections site: synapse
-Information flows: from the dendrites, across the cell body, and down the axon -> AP starts at Axonal hillock
Many axons: wrapped by
an insulating substance – myelin
->Gaps: Nodes of ranvier
->Deposited by glial cells
Axon terminals – communicate with other neurones / muscles (synapses)
Glial cells
Glial cells support neurons
Types:
-Oligodrendrocytes (CNS)
-Schwann cells (PNS)
-Astrocytes (CNS)
-Microglia (CNS)
-Ependymal (CNS)
Oligodrendrocytes (CNS) and
Schwann cells (PNS)
Produce myelin and facilitate transmission
Astrocytes (CNS)
Enable homeostasis, physical
barrier/connector, buffer, reuptake of neurotransmitters support neurones
Microglia (CNS)
Immune cells of the brain
->Phagocytose dead cells and debris
Ependymal (CNS)
Help form barriers
Nerves
Peripheral nerve – sensory and motor (somatic and autonomic) peripheral nerves
->Inside: number of structures containing the axons of a neuron (bundles of axons in PNS)
CNS: Called Tracts = bundle of axons connecting nuclei or regions of the brain
do slides 11 /12 here
Receptor types
- Ligand- gated ion channels (ionotropic) -> milliseconds
- G-protein coupled receptors -> seconds
- Kinase - linked receptors -> mins/hours
- Nuclear receptors -> hours/days
Synapses
May be excitatory
->Stimulus (AP) in second
neurone
May be inhibitory
->Stimulus in 1st makes an AP
less likely to occur
Use different neurotransmitters
-> Allow different ions into the
second neuron
Excitatory synapse
Causes depolarisation
Inhibitory synapse
Causes hyperpolarisation
Synaptic transmission
Synaptic structures are complex
->Multiple synapses onto the same dendrite -> not just 2 neurons in series
-Different synapses can be excitatory or inhibitory
->Whether the neurone fires or not is a sum of all the synaptic inputs
Excitatory neurotransmitters
– Glutamate
– Monoamines -> dopamine, noradrenaline, 5HT/seratonin
– Acetylcholine
Inhibitory neurotransmitters
– GABA
– Glycine
– Endorphins
Other neurotransmitters
Neuromodulators
– Neuropeptides
– Endocannabinoids
Human brain
-Cerebrum
-Diencephalon
-Brain stem
-Cerebellum
Cerebrum
Higher Functions
-Cortex and sub cortex (movement, memory, emotion)
-2 hemispheres joined by corpus callosum
-Surface folded
Cerebrum lobes
-Frontal
-Parietal
-Occipital
-Temporal
Frontal lobe
Reasoning, planning, speech,
movement, problem solving
Parietal lobe
Movement / orientation
recognition, stimuli perception
Occipital lobe
Visual processing
Temporal lobe
Perceptions/recognition of
auditory stimuli
Cerebrum : cortex
-Motor cortex
found in the
frontal lobe
-Sensory cortex
found in parietal
lobe
Diencephalon: Homeostasis
-Between brain stem and cerebrum
-Thalamus
-Hypothalamus and pituitary
Brain stem
Involuntary functions; blood pressure, breathing, vomiting,
sleep/arousal
-Midbrain
-Pons
-Medulla
Cerebellum
co-ordinates movement
CNS: The brain and its protection
Cranium (protection)
Meninges (membranes)
Meninges (membranes)
-Dura mater (outer)
-Arachnoid membrane
-Pia mater (inner)
Cover brain and spinal cord
Between arachnoid and pia
filled with cerebrospinal
fluid (csf)
Protection Cerebrospinal fluid (CSF)
Salty solution secreted into ventricles (chambers in the brain)
Protection
->Physical: buoyancy and padding
->Chemical: Stable ionic environment
-Different to plasma
-No blood cells little protein
