Intro and Homeostasis Physiology - how the body works. Homeostasis - staying the same. Functional Types of Neurons Sensory (afferent - coming in) neurons: Detects the changes in the body. Informations comes to the brain. Interneurons (association neurons): Comprises 90% of neurons. Processes, stores and retrieves information. Motor (efferent - exiting) neurons: Send signals out which result in a response. Functions of Cerebrum (lobes) Frontal: Voluntary motor functions. Motivation. Planning, memory. Mood, emotional and social judgement. Parietal: Taste and some visual processing. Occipital: vision Temporal: Hearing, smell, learning, memory and emotional behavior. Insula: Understanding spoken language. Sense of taste.
Cerebellum Functions Balance, tactile, visual and auditory sensations. Maintains balance and equilibrium by adjusting postural muscles in the body. Fine-tuning movements, performing adjustments to make motor commands smooth.
The Nerve Tissue Neuron - the nerve cell Dendrites - receives information from other neuron cells - input receivers. Cell body - includes usual parts of the organelles of a cell (nucleus, mitochondria) except centrioles --> cannot divide. the cytoskeleton is composed of neurofilaments and neurofibrils. the proteins are synthesized in the cell body and have to be transported to the synaptic terminals. Axon - carries signal towards other cells. the axon hillock is where the signal is first generated. Myelin sheath - a fatty covering that protects the axon and increases conductivity. Synapses - the end of the neuron which transmits the message to other neurons via a chemical and electrical signal.
Classification of Neurons 1. Multipolar neurons: Most common in the CNS. 2. Unipolar neurons: The dendrites and axons are fused (continuous). Cell body lies off to one side. This comprises most of the sensory neurons in PNS. 3. Bipolar neurons: sensory neuron in retina, ear and olfactory system (smell). 4. Anaxonic neurons: Present in retina and CNS. 10 million sensory neurons (pick up any senses to send to brain). 20 billion interneurons (where the processing happens). 500,000 motor neurons (performing an action). Neuroglia - cells that support & protect neurons They make up have the volume of the nervous system. 1. Astrocytes: Gets its name because it looks like the starts (astro). Maintain blood-brain barrier (controlling basically what gets through to the brain). Provides structural support They regulate ion, nutrient and gas concentrations in interstitial fluid. 2. Oligodendrocytes: These are the myelin sheaths - wrap around/insulates the axon. One oligodendrocyte wraps around many neuron axons. 3. Microglia: Related to immune system s cells. They ingest/remove cellular debris and pathogens. 4. Ependymal cells: Are highly branched. Assists in producing, circulating and monitoring cerebrospinal fluid (CSF).
All those above were in the CNS, the PNS contains Satellite cells and Schwann cells. 1. Satellite cells: Surrounds neurons in ganglia. Regulate intercellular 2. Schwann cells: Insulate the axon - similar to oligodendrocytes, but the Schwann cells insulates neurons in the PNS. Myelination, and because its white --> white matter. If the axon is not fully wrapped around by myelin then its an called un-myelinated axon. White matter - regions with myelinated axons. Gray matter - regions with un-myelinated axons.
The areas between the Schwann cells are called Nodes. The Schwann cells themselves are known as Internodes. Neurons perform all communication, information processing and control functions of the nervous system. Neuroglia preserve physical and biochemical structure of neural tissue and are essential to survival and function of neurons. Transmembrane Potential This is due to the unequal distribution of charge across the membrane. When charged particles (Ions) are moving it generates and electrical signal. Inside the membrane is usually slightly more negatively charged. Resting potential - when the cell is not sending any information (-70 mv). Graded potential - when there is a temporary change caused by some type of stimulus. Action potential - electrical impulse produced by the graded potential - it will move across the axon to the synapses - there is a large graded potential. In order to get the neuron to fire/something to happen there needs to be a change in the resting membrane potential of -70 mv (make it more positive). If this happens there will be an action potential. On the plasma membrane of the neuron cell there are K+ and Na+ leakage channels in which Potassium and Sodium ions get leaked through (Sodium moving in and Potassium moving out), and to stop this from happening there is a Sodium Potassium exchange pump. In the sodium potassium pump, for every 3 Na+ there are 2 K+ ions moved. This is all to maintain the concentrated of the resting gradient of -70 mv. The pump is powered by ATP. Passive channels - the leaking channels which are always open. Active channels - the gated channels which open and close, usually closed during rest. The plasma membrane is selectively permeable (very picky).