Lecture 1 Flashcards
Function of Nervous system
Enables rapid and flexible responses to external and internal environmental changes of the body
Sensory function
Senses internal and external changes
Integrative function
Analyses and stores info - Makes decisions on appropriate voluntary and involuntary responses
Motor function
Initiates muscular activity or glandular secretion
Two divisions of nervous system
Central and Peripheral
Central Nervous system roles
- Integrates sensory info
- Generates thought and emotion
- Stores memory
- Makes decisions
- Initiates motor activity
Peripheral nervous system
- Arises from brain/spine
- Carries nerve impulse too and from CNS
- Connects CNS to sensory receptors, muscles and glands
What are neurons?
Electrically excitable cells specialised for signalling
What are glia?
Diverse support and developmental functions
Can neurons divide?
No
Can glia divide?
Yes
Number of glial and neurons in human brain
10^11 neurons and 10^12 glial cells.
Sturctures of neurons
- Cell body - contains normal cell organelles, site of protein synthesis, degradation occurs here
- Dendrites - Short, bristle-like, highly branched processes, recieve nerve input
- Axon - Long, thin process, propagates nerve impulse to other neuron, muscle, or gland, terminates at axon terminal/synpases
Signalling in neuronal cells
- Neurons receive info at dendrites, integrate in cell body
- Info transmitted along axon in the form of electrochemical signals.
- Action potentials are due to ion flow through protein channels
- Lipid bilayer impermeable to charged ions
- At resting potential, concentration of K+ ions is highest inside cell, whilst in Na+ its outside the cell.
- Sodium-potassium pumps use energy from ATP hydrolysis to maintain ionic gradients of sodium and potassium ions across plasma membrane
Stimulation of nerve cells
- Incoming signals depolarise the cell membrane, where membrane potential rises from -70 mV (sodium ion channels open)
- Action potential triggered in axon when cell membrane is depolarised beyond threshold (-55 mV)
- Other signals can hyperpolarise the cell membrane, decreasing the likelihood of an action potential
Properties of Action potentials
- Stimulus produces full action potential, or none
- Impulses jump from node of ranvier to node at myelinated axons at up to 150m/sec
- Signal intensity conveyed by nerve impulse frequency
- Short refractory period where another action potential can’t form
Synapses
- Can be electrical but usually chemical
- Transmitters stored in membrane-bound synpatic vesicles
- 1 amount = quantum
- Action potential arrival causes calcium ion influx, fusion of vesciles with pre-synaptic membrane, release of transmitter into synaptic celft
- Transmitter effect can be excitatory or inhibitory
- Must be mechanism to terminate transmitter’s activity - Catabolism or uptake of neurotransmitter into axon terminal or glial cells
What is behaviour?
An orderly movement with recognizable and repeatable patterns produced by members of a species
Can be homeostasis e.g. maintenance of balance, respiratory rate, heart rate
Any definable set of actions e.g. language, abilities
Examples of behaviour
Courtship, Predation, migration, locomotion, flying, feeding
How can we study human brains?
Neuroanatomy
Clinical studies - lesions
Functional neuroimaging
Studying human brains
Use of diffusion spectral imaging (DSI)
Why use model organisms to understand human brains?
- Strong conservation of genes and function over long evolutionary distances
Manipulation of gene expression - forward genetics
- Identifies gene responsible for phenotype
- Genotype altered to observe effect on phenotype e.g. by random mutagenesis
- Identify mutation/ gene responsible
Manipulation of gene expression - reverse genetics
- Alter specific genes to determine role in phenotype
- Gene sequences identified and altered by site-direct mutagenesis, gene silencing, transgenes
- Determine effect of altered gene on phenotype
