Nervous system
A system of circuits that transmit signals all over the body
PNS: Peripheral nervous system
This includes the spine and all the nerves
in the whole body, like a web of nerves which all end up traveling to the CNS
CNS: central nervous system
This includes the brain which controls
and sort all the signals and forms a response
Neurons:
Dendrites
Cell Body
Axon
Myelin Sheath
Axon terminals
Closest part of the axon to the cell body is call the axon hillock
Glia cells: cells that surround the Neurons and possess multiple functions like insulation, metabolic support and protection
Electrical and Chemical signaling of Neurons
Measured in Milivolts ( mV)
Caused by potential energy caused by the electrical change in the membrane of the Neuron
Outside the Neuron is positive (Na+ and Cl-)
Inside of the Neuron is negative(K+)
When the Neuron wants to send a signal the electro chemical gradients Na and K switch places causing a electrical spark which creates a chain reaction until it reaches the end of the Neuron aka axon terminal to send a signal either chemically or electrically.
It takes energy to move the Na+ outside the cell which creates the potential energy. This process is called Hyperpolarization because it polarizes the cell
When the channels let the Na+ in and K+ out the potential energy is release and this is called depolarization.
Afterwards the channels open again to force the Na+ outside and K+ inside to reset it, this is called Repolarization.
We know the Synaptic cleft as the space between the Terminals and the Dendrites. We also have the presynaptic cell (sends signal) and postsynaptic cell (receives signal)
Electrical signals happen through the cleft if there is a fight or flight signal that needs a very fast response, like running from danger.
Chemical signals through the cleft a slower and happen more casually like your everyday brain activity.
Neuron can respond to many different signals from many other Neurons at the same time, all the signals sum together into what's called Spatial summation
There are Many different Neurotransmitters which work as which control the state of the nervous system chemically, each neurotransmitter can stimulated different parts of the nervous system like the CNS and PNS, bind to receptors etc
Ionotropic receptors are Ligand-gated receptors which require a neurotransmitter to open a ion channel
Metabotropic receptor are G-protein receptors meaning the neurotransmitters bind to the surface which induces a signal intracellularly
All drugs affect the brain in a negative way because the induce a overstimulation or understimmulation of some part of the brain
Most common disorder is Major Depressive Disorder
Some Neurotransmitter damage can lead to motor disfunction like parkinson's disease and multiple sclerosis
Evolution of the nervous system has built into every animal a complex body part with cephalization (aka a brain type structure)
The brain has 3 parts, Hindbrain, midbrain and forebrain
The bigger the Brain and the more folds shows more intelligence if compared to other animals
Body mass is not always proportional to brain mass/intellect
White matter inner brain, myelinated axons bundled together
Gray matter outer brain, mostly neuronal cell bodies and dendrites
Spinal Cord contains Grey matter in the center and white matter around it.
Dorsal roots bring in information and ventral roots bring out information
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Brain is protected by 3 layer of meninges that act as shock absorbers for the brain from the skull also with Cerebrospinal fluid which does a similar job
Somatic Nervous system
Senses the external environments (heat, light, odor, chemicals, Sound, touch) and send signals to the CNS.
This is also allows you to use your muscles to move, voluntary movement.
Autonomic nervous system
Regulates homeostasis, organ function
involuntary functions we cant change it consciously.
Sympathetic division
Rapidly acting responds aka fight or flight activation in means of danger.
Inhibits unnecessary functions like digestion
Increased heart rate, pupils dilated, rush of epinephrine and norepinephrine.
Parasympathetic division
The exact opposite of Sympathetic division, when not in danger the body is relaxed and everything functions as it should.
Forebrain controls Motor, Sensory and Complex functions
Parietal Lobe, interprets motor function
occipital lobe, controls visual perception
Temporal lobe, controls language, hearing and memory
Brain related diseases like meningitis which is a infection that attacks the meninges causing inflammation and pressure in the skull
Alzheimer's disease causes memory loss and cognitive function, caused by age or hereditary
Sensation
Sensory transduction is the process of turning incoming stimuli into electrical signals
Perception is the sensations that we experience conciously
Sensory receptor is either a specialized Neuron or a epithelial cell that synapses with neurons
There is strong and weak stimulus like touching and needle and actually being priked by a needle, the nervous system reacts differently to both.
Type of receptors
Mechanoreceptors: touch, pressure stretch. detected by the hairs on skin and in skin cells
Thermoreceptors: Temperature
Nociceptors: pain, extreme heat/cold, acid burns
Electromagnetic receptors: radiation, UV light etc
Photoreceptors: detect visible light. rods and cones in the eyes
Chemoreceptors: recognized chemicals, in the air water or food etc. Taste buds
Sound is detected by the ear which technically isn't a receptor, cochlea changes vibrations into electrical signals
Defects and disabilities
Eyes problems like blurriness causes by countless reasons
Ear problems causing deafness