Nervous Response

Detect a stimulus.

Impulses are transmitted by a neuron.

Impulses are interpreted and analyzed in the brain or spinal cord.

The response is carried out by an effector, such as a muscle or gland.

Nervous Tissue

Sensory neuron- transmit incoming impulses from sense organs to brain or spinal cord.

Motor neuron- transmit outgoing messages from brain or spinal cord to effector.

Interneuron- pathway between sensory & motor neurons.

Nerves- many neurons grouped together.

Neuron structure

Cell body- cytoplasm & nucleus.

Axon- transmit impulses away from cell body.

Dendrites- transmit impulses toward cell body.

Myelin sheath- outer layer that allows impulse to travel more quickly.

Neuron Junctions

Synapse- small, fluid-filled space between neurons through which the impulse has to cross.

Neurotransmitter- chemicals that are released by axon of a neuron; they transmit impulses across the synapse .

Drugs and the Nervous System

Depressants decrease nerve transmission; results in impaired coordination, slowed reaction time, & impaired judgement.

Stimulants such as caffeine increase nerve transmission causing increased heartbeat rate, blood pressure, & mental alertness.

Nervous Systems

Unicellular organisms

Examples: Bacteria, Protozoan (Euglena, Paramecium)

taxis- movement of an organism toward or away from a stimulus

contain specialized cell parts ( eye spots & flagella) to help respond to the environment

Animals

Porifera: none.

Cnidaria: nerve net.

Platyhelminthes: eye spots; central ganglion.

Nematoda: nerve ring; dorsal and ventral nerve cords.

Annelida: anterior ganglion; ventral nerve cord.

Gastropoda: six pair of ganglion; nerve cord.

Bivalvia: ganglia above mouth and foot.

Cephalopoda: complex brain and eyes.

Echinodermata: nerve ring around mouth.

Crustacea: ganglia connected to ventral nerve cord.

Arachnida: two large ganglia; six to eight simple eyes.

Insecta: chain of ganglia on ventral nerve cord. Hearing, smelling; two compound eyes, up to three simple eyes.

Chondrichthyes: dorsal nerve cord, anterior brain; acute sense of smell.

Osteichthyes: dorsal nerve cord, anterior brain; acute sense of smell; lateral line system.

Amphibia: dorsal nerve cord; anterior brain.

Reptilia: dorsal nerve cord, anterior brain; Jacobsen’s organs used for smell.

Aves: dorsal nerve cord; large brain; color vision; well-developed hearing.

Mammalia: dorsal nerve cord; highly developed brain; most have good vision.

Human Nervous System

Central Nervous System (CNS): brain and one or more nerve cords (spinal cord) which serve as control centers

Peripheral Nervous System (PNS): sensory and motor neurons connected to the CNS

Central Nervous System

Brain

Protected by the skull and meninges (3 layers of membranes)

Fluid fills the cavities of the brain

3 major parts: (forebrain, midbrain, & hindbrain)

Cerebrum

Sensory perception: touch, pressure, temperature, and body position.

Motor Transmission

Integration of information: Consciousness, Language, Emotions, Memory

Cerebellum

Produces skilled movement by coordinating activities of muscle groups.

Helps control posture.

Maintains equilibrium by controlling skeletal muscles.

Brain Stem

Medulla oblongata: vital reflexes and non-vital reflexes.

Pons: regulation of reflexes; cranial nerve reflexes.

Spinal Cord: connects the brain with the PNS.

Surrounded and protected by an extension of the meninges that cover the brain and by a series of bony vertebrate.

Contains a fluid-filled central canal.

Spinal nerves serve as the communication link between the spinal cord and the rest of the body.

Peripheral Nervous System

Sensory- Somatic System

controls responses that are under conscious control

reflexes: involuntary or automatic responses to stimuli

Autonomic System

controls cardiac and smooth muscle

consists of two groups of nerves

sympathetic nerves: prepares body for stress. “fight-or-flight.”

parasympathetic nerves: returns body to normal state. “rest-and-repair.”

Sensory Systems

Ear: senses of hearing and equilibrium.

Ear canal: sends sound waves to ear drum.

Tympanic membrane: ear drum attached to three small bones.

Cochlea: fluid-filled snail-shaped organ used to transmit sound waves.

Semi-circular canals: fluid-filled tubes used in balance.

Eye: sense of sight.

Cornea: clear covering over the eye.

Pupil: opening in the eye that allows light to the retina.

Iris: circular muscle that regulates the size of the pupil.

Lens: disk that focuses light on the retina.

Retina: membrane of photoreceptors at the back of the eye.

Nose: detects chemicals dissolved in mucus membranes.

Seven basic odors: camphorous, musky, floral, ethereal, pungent, putrid, pepperminty.

Tongue: detects chemicals dissolved in saliva.

Four basic tastes.

Sweet: tip of the tongue.

Sour: sides of tongue.

Bitter: back of the tongue.

Salty: sides of the tongue.

Taste buds: taste cells in papilla that detect chemicals.

Skin: contains touch and pressure receptors.

Touch receptors are more concentrated in fingertips, palms, soles of the feet, lips (areas of skin with no hair).

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