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The Nervous System
Transcript of The Nervous System
This causes the membrane to be electrically charged.
The difference of charge comes from:
Selective permeability of the cell membrane
Mainly the active transport of ions across the membrane
The membrane allows more K+ to leak out, making the inside of the cell negative. The Nervous System Farah Hashmi
Stephanie You Nervous System: Controls and coordinates the body and responds to stimuli Impulses Electrical signals/ messages carried by the nervous system Neurons Transmit impulses Types of Neurons -Sensory Neurons
Sense organs the spinal cord and brain
The brain and spinal cord muscles and glands
Sensory neurons motor neurons Parts of a Neuron Cell body: largest part, contains the nucleus and much of the cytoplasm
Dendrites: extensions of the cell body that carry impulses from the environment or from other neurons toward the cell body.
Axon: long fiber that carries impulses away from the body Axons + dendrites = nerves Impulses jump from node to node. Resting Neurons No impulses Resting potential: the electrical charge across the cell membrane of a neuron in its resting state.
The neuron isn't actually resting though. It is constantly producing ATP for active transport.
Remains at rest until a large stimulus starts a nerve impulse An impulse The impulse travels At the leading When the impulse that begins when a neuron is stimulated by another neuron or the environment causes the movement of ions across the cell membrane. down the axon away from the cell body and toward the axon terminals. edge of an impulse, 1000s of protein channel gates in the cell membrane open, and Na+ goes in the cell. The inside of the cell becomes more positive, reversing the potential. An impulse is the sudden reversal of membrane potential, and it is also called action potential. begins to pass, the gates open, and K+ is transported out of the cell. The inside of the cell becomes negative once again, going back to the beginning of the cycle. An impulse at The Moving Impulse any point on the membrane causes an impulse at the next point on the membrane, and all impulse strengths are the same. The Domino Effect Threshold The minimum level of a stimulus that is required to create an impulse. The Synapse The impulse reaches an axon terminal at the end of the neuron.
The neuron can pass the impulse to the next cell.
Synapse: where a neuron can transfer an impulse to another cell
Synaptic cleft: separates the axon terminal from the dendrites of the next cell.
The axon terminals contain vesicles filled with neurotransmitters.
Neurotransmitters: chemicals in a neuron that transmit an impulse across the synapse. Neurotransmitters are released into the synaptic cleft when an impulse arrives at the axon terminal
The neurotransmitters diffuse across the synaptic cleft and attach themselves to receptors on the next cell's membrane.
This causes Na+ to enter the next cell
If the stimulation passes the cell's threshold, a new impulse is created.
The neurotransmitters are released and either broken down by enzymes or recycled by axon terminals. Drugs Any substance that changes the structure or function of the body Stimulants increase the actions regulated by the nervous system Depressant Cocaine Opiates Mimic natural chemicals in the brain called endorphins, normally helping to overcome sensations of pain. Causes sudden release of neurotransmitters in the brain called dopamine Marijuana Long term can cause memory loss and inability to concentrate Decreases the rate of functions regulated by the brain Also a powerful stimulant Alcohol Most immediate effects are on the central nervous system
Depressant that slows the functioning rate of the central nervous system Sensory Receptors neurons that react to a specific stimulus by sending impulses to other neurons and eventually, the central nervous system
Concentrated around the sense organs Pain Receptors located everywhere except the brain
Respond to chemicals released by damaged cells
Important for indicating danger, injury, and disease. Thermoreceptors located in skin, body core, and hypothalamus
detect temperature changes Mechanoreceptors located in the skin, skeletal muscles, and inner ears
Sensitive to touch, pressure, stretching of muscles, sound, and motion Chemoreceptors Located in the nose and taste buds
Sensitive to environmental chemicals Photoreceptors Sensitive to light
Located in the eyes
Rods: extremely sensitive, but no color
Cones: less sensitive, but responds to color Nervous System: Two Divisions The Nervous System is divided into two main divisions: The Central Nervous System and the Peripheral Nervous System. Central Nervous System: the control center of the body. It relays messages and also processes and analyzes information.
Peripheral Nervous System: It receives information from the environment and relays commands from the Central nervous system to other organs and glands. Central Nervous System: Consists of the brain and spinal cord. The skull and vertebrae protect these parts.
Both parts are wrapped in 3 layers of tissue known as meninges
Cerebrospinal fluid: liquid that fills in space between meninges and central nervous system. Acts as shock absorber and allows the exchange of nutrients/waste between blood and nervous tissue. Brain: Where impulses flow and from which impulses originate.
Contains about 100 billion neurons (most of which are interneurons). The brain is broken into different parts: the Cerebrum, Cerebellum, Brain Stem, Thalamus and Hypothalamus. Brain Stem Connects the brain and the spinal cord
Includes two regions: pons and medulla oblongata
These regions act as a neural "switchboard"- it regulates the flow of info between brain and body
Important function of the body are controlled by the brain stem (blood pressure, heart rate, breathing, etc.) Cerebrum Cerebellum The second largest portion of the brain
located at the back of the skull
It coordinates and balances the actions of the muscles so that the body can move gracefully and efficiently Thalamus and Hypothalamus Both found between the brain stem and cerebrum Thalamus: Receives messages from all of the sensory receptors throughput the body and then relays information to the proper region of the cerebrum for further processing Hypothalamus: Control center for recognition and analysis of hunger, thirst, fatigue, anger, and body temperature. Aslo controls coordination of nervous system and endocrine system. Spinal Cord The main communication link between the brain and the rest of the body
31 pairs of spinal nerves branch out from the spinal cord and connects the brain to all the different parts of the body.
Reflexes are processed directly in spinal cord. Reflex: quick, automatic responses to a stimulus. Allows the body to react to danger immediately without thinking about a response. The largest region of the brain
Responsible for voluntary activities of the body
It is also the site of intelligence, learning, judgement, etc.
Deep grooves divide cerebrum into right and left hemispheres
the band that connects these hemispheres is called the corpus callosum. The folds/grooves on the surface of each hemisphere greatly increases the surface area of the cerebrum.
Each hemisphere is divided into regions called lobes, which are named after the skull bone that cover them. Each half of the cerebrum deals mainly with the opposite side of the body.
Sensations from the left side of the body go to the right hemisphere and vice versa. Opposite Sensations Right Hemisphere: creativity/ artistic ability
Left Hemisphere: analytical/ mathematical ability Multilayered The cerebrum has two layers: the outter layer and the inner layer Outer Layer: contains the cerebral cortex, which consists of grey matter- densely packed nerve cell bodies. It also processes information from sense organs and controls body movement.
Inner layer: made up of white matter- bundles of axons with myelin sheaths. Myelin sheaths give white matter its color. White matter connects the cerebral cortex and the brain stem Peripheral Nervous System Lies outside of the Central Nervous System
Consists of all nerves and associated cells not part of the brain or spinal cord.
Contains cranial nerves (which pass through openings in the skull) and ganglia.
Ganglia: collection of nerve cell bundles. Division The Peripheral Nervous System is divided into two parts: the sensory division and the motor division. Sensory Division: transmits impulses from sense organs to the central nervous system.
Motor Division: Transmits impulses from the Central Nervous System to muscles and glands in the body. These are further divided into somatic and autonomic nervous systems. Somatic Nervous System Regulates activities that are under conscious control
Controls movement because of motor neurons
Some neurons involved with reflexes and can act without conscious control
Rapid responses before/ during pain is possible because receptors in the skin stimulate sensory neurons, which carry impulses up to the spinal cord and automatically activates appropriate motor neurons. Autonomic Nervous System Regulates activities that are automatic/ involuntary
Controls functions of the body not under conscious control
It is divided further into two parts: sympathetic and parasympathetic nervous systems. Most organs controlled by the autonomic nervous system are under the control of both. Sympathetic and parasympathetic nervous systems have opposite affects on the same organ.
These opposing effects of the two systems help maintain homeostasis in the body. Axon terminals: a series of small swellings at the end of an axon
Myelin sheath: insulating membrane that sometimes surrounds the axon
Nodes: gaps that are left by the myelin sheath where the axon is exposed.