We prevent large changes from cell contents by buffering with extracellular fluid for homeostasis to occur. We also
control body systems through extracellular fluid (where all sensory systems take place) and intracellular fluid, both
containing ion concentration.
Homeostatic mechanism
You cannot generate a receptor without a stimulus, once the stimulus activates the receptor it goes through the
afferent pathway, integrating center, efferent pathway, effector organs containing muscles and organs to then
stimulate a response to a positive or negative feedback
Dendrites bring information into the body by forming synapses for communication. The axon takes information
away from the cell body. Where the action potential gets generated is at the axon hillock. The end of the axon has
neurotransmitters to transfer electric alchemical signals. Nodes of Ranvier pass electrical current quickly in the
axon.
Afferent neurons use interneurons to bring sensory information to the CNS. Efferent neurons take information
from the CNS to produce a response outside the body.
There are two major division of the nervous system. The central nervous system (CNS) and the peripheral nervous
system (PNS). The central nervous system is composed of two structures: the brain and spinal cord. The spinal cord
has gray matter while the brain has white myelinated matter or, ascending and descending pathways. The spinal
cord is composed of the dorsal and ventral root. The dorsal root having ganglion, brings information in to the
spinal cord then to the spinal nerve while the ventral root takes information out of the spinal cord having no
ganglion meaning no cell bodies. The brain is subdivided into three main sections the forebrain, brainstem and
cerebellum. Our forebrain is what makes us different. The forebrain is divided into the cerebral hemispheres and
diencephalon. The 4 cerebral hemispheres are the frontal dealing with motor cortex, parietal on the side of the
head dealing with touch, pressure and taste, occipital in the back of the head dealing with visual and temporal near
the ear dealing with auditory and olfactory. The diencephalon is subdivided to the thalamus or integrating rely
center while the hypothalamus deals with internal physiological responses such as eating and drinking. The brain
stem is the second section of the brain consisting of the midbrain, pons, medulla oblongata and reticular formation
which gives consciousness. Lastly the cerebellum is also called the little brain dealing with coordination such as
movement and balance
The PNS contains the cranial and spinal nerves that run throughout the body. Both having afferent and efferent
pathways. The PNS is made up of two subdivisions, firstly, the somatic nervous system which contains nerves that
carry sensory signals from the body to the CNS and nerves that carry motor signals from the CNS to the skeletal
muscles. The somatic NS is associated with voluntary movement. The second division of the PNS is the autonomic
nervous system (ANS) or involuntary nervous system which is involved in regulating the internal environment of
the body. The ANS is further subdivided into the sympathetic and parasympathetic nervous system. The
sympathetic nervous system dealing with fight or flight with the help of our adrenergic system while the
parasympathetic acts to conserve energy with the help of our cholinergic system or rest and recovery.
Membrane potentials are calculated by Goldman
Refers to the difference of electrical charges across the cell membrane
Equilibrium potential is determined by Nernst equation which calculates the voltage necessary to oppose the net
movement of an ion down its concentration gradient. It is the membrane potential at which electrical chemical
gradient are equal or the voltage required to maintain concentration gradient
If we have more potassium inside, we get a positive equilibrium
If we have more sodium outside, we get a positive equilibrium
Increase in Na permeability = depolarize
Increase K permeability = hyperpolarize because we are moving towards equilibrium values
