Nervous System PPT

Topic: Nervous System

Technical English Lic. Carlos Contreras

Today’s agenda 2022

Dec. 5th,

Greetings Topic “The Nervous System” Objective: Activity “Group work activity” Wrap up “ What did you learn?” Homework

The Neuron

• Dendrites receive signals.
• The cell body integrates signals.
• The axon transmits action potential. The myelin sheath makes the signal travel faster.
• Synaptic terminals transmit signals.

Synapse

• Neurons usually do not connect directly to one another. A gap called a synapse controls the transmission of signals.
• Neurotransmitters cross the synapse and stimulate the next neuron.

Some Neurotransmitters

Neurotransmitter

Location

Some Functions

Acetylcholine

Neuron-to-muscle synapse

Activates muscles

Dopamine

Mid-brain

Control of movement

Stress response

Epinephrine

Sympathetic system

Serotonin

Midbrain, pons, medulla

Mood, sleep

Endorphins

Brain, spine

Mood, pain reduction

Nitric Oxide

Brain

Memory storage

Information Processing

Four basic operations

• Determine type of stimulus
• Signal the intensity of a stimulus
• Integrate responses from many sources
• Initiate and direct operations

Why a Brain?

• Brains are the result of selection for centralization of the nervous system.
• Neurons control movement. The brain (or spine) interprets sensory signals and determines the appropriate movements (that is, behavior).
• Appropriate movement is critical to the survival of most animal species.

Nervous System

Neural Organization

Central Nervous System

Consists of brain and spineFunctions:

• Receives sensory signals and determines appropriate response
• Stores memory
• Carries out thought

Spine: structure

• The spinal cord is protected by the vertebrae.
• Gray matter contains cell bodies; white matter contains myelinated fibers.
• PNS nerves extend outside of the vertebrae.

Brain: Structure

• Hindbrain carries out the most basic functions.
• Midbrain coordinates signals.
• Forebrain processes signals, stores memories, creates thought.

Peripheral Nervous System

Nerves, neurons, and sensory organs outside the central nervous systemFunctions:

• Sends signals to the CNS
• Receives and transmits motor signals from the CNS
• Stimulates effectors

Somatic Nervous System

• Motor neurons that control voluntary movements by activating skeletal muscles.
• Also involved in what we perceive as involuntary movements, such as reflexes (though voluntary control of the muscles involved, such as tensing them, can reduce the response).

Autonomic Nervous System

• Motor neurons that control involuntary responses involving the organs, glands, and smooth muscles.
• Some voluntary control over the responses can come from relaxation, meditation, etc., which reduce perceptions of stress and in turn reduce the stress response.

Sympathetic Division

• Portion of the autonomic nervous system that produces the “fight or flight” response:
• Dilation of pupils
• Increased heart and breathing rates
• Constriction of blood vessels
• Inhibits digestion

Parasympathetic Division

• Portion of the autonomic nervous system that produces the “rest and ruminate” response:
• Constricts pupils
• Dilates blood vessels
• Reduces heart and breathing rates.
• Stimulates digestion.

The Complex Brain

• The mammalian brain is highly complex, containing many specialized regions that carry out specific functions.
• Generally, the brain is divided into hindbrain, midbrain, and forebrain.

Hindbrain

• Medulla: controls autonomic fuctions.
• Pons: controls sleep stages.
• Cerebellum: coordinates movement, stores some motor memory.

Midbrain

• Reticular formation: the “traffic cops” of the brain.
• Filters sensory input, which allows us to concentrate.
• Filtering can be affected by higher thoughts.

Forebrain

• Thalamus: relay station channeling sensory information.
• Limbic system: basic emotions, drives, and behaviors.
• Cortex: higher thought

Limbic system

• Hypothalamus: master controller of the endocrine system.
• Amygdala: sensations of pleasure or fear, recognition of fear in others.
• Hippocampus: formation of memories.

Cortex

• Various areas control sensory processing, motor control, thought, memory.
• Wiring is plastic: people blind from birth, for example, use parts of the visual cortex to process auditory signals.

Left brain, right brain?

• While there is some specialization to each hemisphere, the idea has been oversimplified.
• The left brain controls the right half of the body; the right brain controls the left half of the body.
• However, “right brain” or “left brain” functions such as math, language, etc. produce activity on both sides of the brain, and processing of these may be different in different people (males vs. females, novices vs. experts, etc.).

Brain “maps”?

While hemispheric research shows some specialization between hemispheres, most “brain maps” like this are nonsense.

“Flavor”

• What we sense as the “flavor” of food is not taste alone. Smell and taste together create the sensation of “flavor.”
• This is why things don’t “taste” good when we have a cold; we lose the sense of “flavor.”