NERVOUSNERVOUS SYSTEM SYSTEM

Science, Technology, & SocietyMR. CANOVA

Period 11

Neurons and Nerve ImpulsesNeurons and Nerve Impulses

Neuron-Nerve cells that transmit information throughout the body

Dendrites-”Antennae” that receive information from other cells

Axon-Extension of cytoplasm that conducts nerve impulses

Myelin sheath-Layer of insulation

Nodes of Ranvier-Gaps between myelin sheath

Neuron FunctionNeuron Function

Membrane potential- The difference in electrical charge across the cell membrane. Expressed in voltage.

Resting potential- The membrane potential of a neuron at rest -70 millivolts (mV) Inside of cell is negatively charged, outside of cell is positively

charged K+ ions in the cell, Na+ out of the cell

Action potential- A nerve impulse Approaches +40 millivolts (mV) Inside of cell is positively charged, outside of cell is negatively

charged Na+ ions in the cell, K+ out of the cell

Communication between NeuronsCommunication between Neurons

Synapse: The junction where a neuron meets

another cell• Pre/Post synaptic cell

Neurotransmitters: Signal molecules that bind to

receptor proteins on the postsynaptic cleft and interact wit the postsynaptic cell

• Can excite or inhibit the activity of a cell it binds to

Membrane potential: + ions enter neuron, an

action potential is produced (excitation)

- ions enter neuron, an action potential is suppressed (inhibition)

Central Nervous SystemCentral Nervous System

Consists of the brain and the spinal cord.

Interprets and responds to information from the environment and from within the body.

BRAIN- The body’s main processing center. Contains about 100 billion neurons.

Cerebrum- The largest part of the brain Cerebellum- At the base of the brain,

regulates balance, posture, and movement.

Brain stem- At the base of the brain, a collection of structures leading to the spinal cord.

• Upper- Thalamus and Hypothalamus

• Lower- Midbrain, Pons, and Medulla oblongata

SPINAL CORD- A dense cable of nervous tissue that runs through the vertebral column.

THE BRAINTHE BRAIN

SPINAL CORDSPINAL CORD

Peripheral Nervous SystemPeripheral Nervous System

Consists of 31 spinal nerves and 12 cranial nerves.

Connects the brain and the spinal cord to the rest of the body

2 Divisions: Sensory and Motor Sensory-Directs sensory information to the CNS Motor-Carries out responses to sensory information.

2 Principal Divisions:• Somatic and Autonomic Nervous systems

Somatic-Reflexes, some are involuntary Autonomic-Involuntary responses

2 Divisions:• Sympathetic and Parasympathetic

Sympathetic- Under stress • (Fight or Flight responses)

Parasympathetic- Normal conditions • When body is at rest (ie-sleep)

SENSORY RECEPTORS

Receptor type Stimuli LocationsThermoreceptors Temperature change Skin, Hypothalamus

Pain receptors Tissue damage Tissues and Organs

Mechanoreceptors Movement, Pressure, Tension

Skin, Ears, Muscles

Photoreceptors Light Eyes

Chemoreceptors Chemical Tongue, Nose

Processing of Sensory InformationProcessing of Sensory Information

4 main lobes- Frontal

• Motor function• Intellectual function• Speech• Smell

Occipital• Vision

Parietal• Sensory• Taste

Temporal• Hearing

THE EYETHE EYE

Pupil-Allows light to enter the eye

Lens-Disk that focuses light onto retina

Retina-Lining on back of the eye that converts light energy into electrical signals

Cornea-Transparent covering on eye

Iris-Controls amount of light that enters the eye

Rods-Respond to dim light Cones-Respond to bright light

and allow color vision Optic nerve-Exits back of the

eye and runs along base of the brain to the thalamus

THE EARTHE EAR

Eardrum-Vibrates when sound waves enter

Middle ear-Consists of 3 small bones; hammer, anvil, and stirrup

Cochlea-Fluid-filled chamber that contain hair cells that generate nerve impulses.

Auditory nerve-Sends impulses to the brain

Semicircular canals-Fluid-filled chambers in the inner ear that maintain equilibrium

Located above cochlea

CHEMICAL SENSESCHEMICAL SENSES

CHEMORECEPTORS- LOCATED ON THE

TONGUE• 4 CHEMICAL

SUBSTANCES

OLFACTORY RECEPTORS- LOCATED IN THE

NASAL PASSAGE• Sense of smell

Drugs and the Nervous System

Drug Examples Psychoactive effects

Depressants Alcohol, Sedatives Decreased CNS activity

Stimulants Cocaine, Crack, Nicotine Increased CNS activity

Inhalants Paint thinner, Glue Disorientation,Confusion

Hallucinogens LSD, PCP, MDMA Anxiety, Hallucinations

THC Marijuana, hashish Short-term memory loss

Narcotics Heroin, Morphine, Codeine, Opium

Sedation

Drug Addiction and Neuron FunctionDrug Addiction and Neuron Function

Addiction- Physiological response caused by use of a drug that alters the normal functioning of neurons and synapses.

Tolerance- Increasing amounts of the drug are needed to achieve the desired sensation.

Withdrawal- Emotional and physical symptoms caused by removal of the drug from the body.

Depressant- Drug that decreases the activity of the CNS

Stimulant- Drug that increases the activity of the CNS