lecture 1 notes

Lecture 1: 

Homeostasis 

• Maintain system in a narrow range  

• Brain gets info by sensory input which are action potentials from receptors  

CNS 

• Where processing and relaying information occurs (brain + spinal cord) 

• Glia cells in CNS are : oligodendrocytes (can myelinate multiple axons), astrocytes (provides nutrients and maintain extracellular environment as well as structural support), microglia (immune response), ependymal cells (circulate and produce cerebrospinal fluid)  

PNS 

• Where sensory stimulus is picked up and is turned into AP to send towards CNS 

• Glia cells in PNS are : schwann cells (forms myelin for one axon), satallite cells (provides nutrients and structural support to neurons) 

Nerve cells (neurons) 

• Has an input zone, summation zone, conduction zone and an output zone  

• Inputs and outputs from a neuron can be excitatory or inhibitory  

• Information processing in the nervous system is the throughput and balance of excitatory and inhibitory signals across networks of neurons  

Axons and nerves  

• Nerves are made up of many axons and they could be myelinated or unmyelinated  

• Axons are sometimes called nerve fibres  

Synapses  

• Electrical synapse --> very fast and ions flow from cell to cell (may be bidirectional) 

• Chemical synapse --> slower, relies upon chemical crossing the gap, complex series of events, neurotransmitter packaged in vesicles and synapse strength can be modified (are unidirectional) 

Brain is organized into regions based on function 

• Sensory axons from all body locations retain a strict spatial relationship to one another along their projection pathways and info arrives in somatosensory cortex. Sensory map distorted based on their high receptor density (based on how sensitive a part of the body is) 

Information flow  

• Afferent --> info flowing towards the CNS (brain) 

• Efferent --> info flowing away from CNS 

• Enteric NS are in walls of the digestive system  

• Signalling within a single nerve cell is electrical; electrical potential across the membrane of an inactive nerve cell is the resting membrane potential  

• Signalling between nerve cells or between nerve and non-nerve cells are mostly chemical