Nervous System Flashcards
Functions of the Nervous system
- Integrate multiple inputs to sense changes in internal/external enviro
- Initiate adaptive responses from body systems (voluntary/involuntary)
- More sophisticated functions (memory, anticipation, learning and co-operation)
Cells of central nervous system (6)
- Nerve cells (neurons)
- Glial cells (glia)
- Oligodendrocytes
- astrocytes
- microglia
- ependymal cells
Basic structure of neuron
-Dendrites, soma, axon hillock, axon, axon terminal
- Dendrites: receive input signals from other neurons
- also increases SA - Soma (cell body): housekeeping functions (nucleus to store genetic material, ER, mitochondria - energy)
- uses 20-25% of body’s energy - Axon hillock: Synaptic integration, action potential triggering
- Axon: conveys electrical output signals (action potentials)
- Axon terminal: Specialised to release transmitter (chemical) to signal to next cell in pathway
Neuron definition
- Specialised to receive, integrate and transmit information to other cells
- info transmitted as a chemical and/or electrical signal
Classification of neurons by location
- Central nervous system
- brain and spinal cord
- Peripheral nervous system
- outside brain and spinal cord -> includes cranial and spinal nerves
- any neuron that sends a process out of CNS
Classification of neurons by function
- based on where neurons taking info to/from
- Interneuron: are connecting neurons whose processes are restricted to a particular CNS region -> allow increased complexity of network activity
- Afferent Neuron: From sense organ to integrating centre
- Efferent Neuron: from integrating center to effector organ
Classification of neurons by structure
-Fascicle and nerve definition
- based on number of processes arisng from soma
- Multipolar, bipolar and unipolar
- Fascicle: bundles of axons from many different neurons
- Nerves: are bundles of fascicles
Glial cells - functions/role
- Make up more than 90% of cells in CNS
- Physically support neurons - also have housekeeping functions
- Cannot fire action potentials
- Can influence synaptic transmission
5 Glial cells and their functions
-Myelin definition
- Schwann cells: form myelin (PNS)
- Oligodendrocytes: form myelin (CNS)
- Astrocytes: transport nutrients to neurons
- also form blood brain barrier - Microglia: Remove debris/dead cells from CNS (derived from macrophages)
- Ependymal cells: line fluid filled cavities of CNS
Myelin: layers of lipid-rich glial cell plasma membrane, provides electrical insulation for nerve axons
Evolution of nervous system
- Radially symmetrical animals
- Bilaterally symmetrical animals
- Almost all multicellular organisms have nervous system
- Radially symmetrical animals (e.g. corals, jellyfish) have nerve nets - scattered neurons, diffuse connections
- no clear afferent/efferent division (no integrating centre - Bilaterally symmetrical animals (like humans - and most other animals)
- emergence of ganglia (act as integration centres)
- cephalisation increases w/ increasing nervous system complexity (tendency for integration centers and sense organs to be clustered at anterior end)
Features of vertebrate nervous system (4)
- Highly cephalised
- Part of nervous system (CNS) encased w/in cartilage or bone
- Dorsal nerve cord
- Hollow nerve cord (Contains CSF)
- nerve cord = brain and spinal cord
- Brains have same basic parts - expanded or reduced depending on functional requirements
Seven regions of the vertebrate central nervous system
- Spinal cord
- Cerebellum
- Medulla
- Pons
- Midbrain
- Diencephalon (thalamus and hypothalamus)
- Cerebrum
Spinal cord
Cerebellum
Spinal cord:
-somas in the center (grey matter), axons around the outside (white matter)
-main function is mediating reflex arcs
-sensory nerves in dorsal horn, motor in ventral horn
Cerebellum:
-integrates sensory, motor and vestibular (balance) inputs
-Functions include learning motor skills, co-ordination, eye movements and maintaining posture
-loads of neurons
Brainstem: Medulla, pons, midbrain
- Medulla Oblongata: regulation of blood pressure, digestion and breathing
- Pons: relays info between cerebellum and cortex
- regulates breathing, sleep - Midbrain: controls sensory functions (visual, auditory, touch)
- controls reflex responses to sensory input
Diencephalon - 2 main divisions
- 2 main divisions;
1. Thalamus: relay station, controls transfer of sensory info from periphery to cortex
2. Hypothalamus: regulates hormonal secretions of pituitary gland, regulation of circadian rhythms, important in motivation
Cerebrum
-Corpus callosum
- cerebral cortex = info processing (cerebral hemispheres)
- deep structures
- basal ganglia: fine movement control
- amygdala: social behaviour and emotion
- hippocampus: memory
- basal ganglia: fine movement control
*Corpus callosum: larg tract of axons that links left and right hemispheres of brain
Cerebral cortex and 4 hemispheres
- Thin, outermost layer of cerebrum -> performs the highest lvl of info processing
- 4 lobes: frontal, temporal, parietal and occipital
- neuron numbers and cortical infoldings (sulci) tend to increase through evolution
Definitions;
- Electricity
- Charge - and two types
- Potential differences
- when current will flow (2 requirements)
- Electricity: Presence and flow of electrical charge
- Charge: a physical property of matter, which means the matter experiences a force if it encounters other charge material
- two types; positive and negative
- Difference in charge between two places = potential difference (measured in volts)
- net movement of charge = current (measured in amperes - amps)
- current will flow if two places with a potential differences are connected by a conductor
- Electrons and ions
- 2 types of ions
- Electrons: what carries a current in a wire (negatively charged)
- Ions: what current is carried by in a solution
- 2 types;
- Cations: positive ions
- Anions: negative ions
- 2 types;