Nervous System

Spinal cord is a nerve tissue that extends from the skull throught the backbone

relays infor between body and brain, is protected by mengies, cerebrospinal fluid and vertebrae

Brain

GREY matter of the brain is unmyelinated

WHITE matter of the brian is myelinated

Skull and mengies protect it

1. Forebrain
2. Midbrain
3. Hindbrain

Midbrain processes sensory input from eyes and ears and relays info the other areas of brain

Hindbrain is used for coordination and maintaining homeostatic functions

Cerebellum is used for controlling limb movements, balance, fine motor skills and reflexes

Pons passes info btw neurons of left and right halves of brain

Medulla Oblongata joins the spinals cord to the cerebellum Nd the PNS and CNS; coordinates homeostasis

Forebrain is used for through, learning and emotions

Thalamus is located at baseof forebrain and provides connection btw parts of the brain

hypothalamus located below thalamus contains neurons that control homeostasis

Cerebrum is the largest part of the brain and is divided into two hemispheres and 4 lobes

Right lobe controls sensory stimilus and motor control of/from left side of body

Left lobe controls stuff on right side of body

Frontal Lobe:
integrates info from other parts of brain and controls reasoning, critical thinking, memory and personality

Temporal Lobe:
shares processing of visual info main function is auditory reception

HIppocampus: used in learning and memory

Parietal Lobe:
receieves and processed sensory info from the skin and processes info about orrientation

Occipital Lobe:
analyzes visual info and recognition of what is being seen

Blood Brain Barrier

Selectively controls the diffusion of substances into the brain from the blood

Cerebrospinal fluid is a liquid derived from blood plasma circulating throught the spaces between the brain and spinal cord

provides shcok absorbtion and transports hormones, wbc and nutrinets across the BBB

Sensory pathways include afferent transmissions of impuses from peripheral organs to the CNS
Motor pathways are efferetn transmissions of impulses from CNS to peripheral organs

Somatic is action which requires conscious thought before hand and when the signals take a longer path to the effectors and autonomic is for all actions which do not require conscious thought and in which the signal goes straight from stimilus to effector ex. Reflexes and homeostasis

Autonomic system

Sympathetic nervous system is for all fight or flight responses and falls beloww the autonomic division

Parasympathetic is responsible fro rest and digest functions which is used to maintain homeostasis (acetylcholine is used to commence this function) this also falls under autonomic system

Reflex arc:
nerve pathway containing 5 components
- receptor
- sensory neruon
- interneuron in spinal cord
- motor neuron
- effector

All occurs without the signal going to the brain
ex. touching a hot stove, knee jerk,

Cells:
- Neurons
- Giial Cells

Types of Neurons:
1. Sensory Neurons
2. Interneurons
3. Motor Neurons

Motor neurons relay information form the CNS to PNS and effectors

Sensory neurons sense and relay info from PNS to CNS for processing

Interneurons link sensory and motor neurons and exisit only in the CNS

Neurons:
- Dendrites
- Axon
- Axon Terminals
- Mylein Sheath
- Schwann Cells
- Nodes of Ranvier
- Cell Body

Dendrites Recieve information from receptors or nerve cells

Axons and Axons terminals carry nerve impulses away from cell body to other neurons/effectors

Cell body contains the genetic info, specialized organelles, nucleus and maintains the structure of the neuron

Mylein Sheath is a fatty layer surrounded the axon allowing nerve impluses to travel faster

Schwann Cells are a type of gilal cell that produces the mylein sheath

Nodes of ranvier are gaps in the mylein sheath which allow nerve impulses to jump from on node to another

Membrane potential is the potential energy across a cell membrane

Resting membrane potential:
nerves are not transmitting brain impluses

membrane potential of -70mV is fored as a result of the chemical gradient formed by the constant pumping of Na+/K+

3 factors play a part in maintaing the resting potential:
1. negative proteinss inside the cell
2. ion specific channels allowing passive movement
3. sodium/potassium pump brining 3Na+ out and 2K+ in resulting in a positive charge OUTSIDE of the cell

Action potential is a change in potential from resting state

when signal is recieved in dendrites gates open in the neurons membrane allwing Na+ to move into the cell. if the charge reaches above approx. 55mV the neuron becomes active and the action potential begins

All or nothig principle reffers to wheter the signal from a neuron is sufficient enough to reach the threshold of excitation

4 stages of action potential:
1. resting state
2. Depolarization
3. Repolarization
4. Hyperpolarization
refractory period

Resting State:
Lots of sodium inside lots of potassium inside
-70mV

Depolarization
Na+ channels open and na moves in
K+ channels are closed
-50mV

Repolarization:
+40mV
na channels close
k+ channels open and k moves out of cell

Hyperpolarization:
K+ continues moving out of the cells until it becomes -90mV then K+ channels close

Refractory period:
both channels are closed and protein retores -70mV

Synapse:
can be chemical and electrical
signal transmission occurs at the junction between two neurons (place where neurons communicate with each other

NEUROTRANSMISTTERS carry neutral signal from one neuron to another

exictatory ion channels open to allow Na+ in to depolarize

Inhibitory allow k+ to flow out to hyperpolarize cell