Abcte Biology

Front 1

neurons

Back 1

the fundamental unit of the nervous system, having structure and properties that allow it to conduct signals by taking advantage of the electrical charge across its cell membrane

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neurons are classified into 3 types according to the directions in which the impulses move

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1. Sensory neurons carry impulses from the sense organs to the brain and spinal cord.
2. Motor neurons carry impulses from the brain and spinal cord to muscles or glands.
3. Interneurons connect sensory and motor neurons and carry impulses between them.

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largest part of the neuron

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cell body which contains the nucleus and most of the cytoplasm; therefore, most of the cell's metabolic activities occur here.Spreading out from the cell body are branched extensions called dendrites. They carry impulses toward the cell body. The long fiber that carries impulses away from the cell body is the axon, which ends in a series of swellings called axon terminals.

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dendrites

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Spreading out from the cell body are branched extensions. They carry impulses toward the cell body

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axon terminals

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The long fiber that carries impulses away from the cell body is the axon, which ends in a series of swellings

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nerves

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bundles of neurons. The nerves contain a large number of independent communications channels. They are also composed of many supporting cells that form nervous tissue. Schwann cells wrap around axons forming a fatty, insulating covering called a myelin sheath. There are small gaps, called nodes, between the myelin sheaths. As an impulse moves down an axon, it will jump from node to node. This increases the speed of the impulse.

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myelin sheaths

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Schwann cells wrap around axons forming a fatty, insulating covering

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nodes

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There are small gaps between the myelin sheaths

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nerve impulse

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a flow of electrical charges along the cell membrane of a neuron. The strength of an impulse must reach a minimum level of a stimulus to activate a neuron is the threshold.

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recepto

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special sensory neurons in sense organs that receive stimuli from the external environment

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effector

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muscles or glands that bring about a coordinated response

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synapse

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The space between neurons where an impulse is passed from one cell to another

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neurotransmitters

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Tiny vesicles located in the axon terminal are filled with chemicals

Front 14

Which type of neuron is responsible for transmitting impulses to the central nervous system?

A Sensory neuron
B Interneuron
C Receptor neuron
D Motor neuron

Back 14

A is the correct choice, because sensory neurons carry signals from sense organs to the brain and spinal cord. Interneurons connect sensory and motor neurons and carry impulses between them. Receptor neurons are special sensory neurons in sense organs that receive stimuli from the external environment. Motor neurons carry impulses from the brain and spinal cord to muscles or glands.

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The 2 major divisions of the human nervous system

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central nervous system and the peripheral nervous system

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central nervous system

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serves as the control center of the body. It consists of the brain and the spinal cord. Its functions are relaying messages, processing information, and comparing and analyzing information.

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peripheral nervous system

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consists of everything but the brain and spinal cord including the cranial nerves, and nerves of the neck, chest, lower back and pelvis.

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meninges

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the brain is wrapped in 3 layers of connective tissue

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pia mater

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innermost layer of connective tissue is bound to the brain

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arachnoid

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the middle layer of connective tissue surrounding the brain

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dura mater

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outermost layer of connective tissue surrounding the brain

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cerebrum

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The largest part of the brain. It is responsible for all of the voluntary activities of the body. It is also the sight of intelligence, learning, and judgment.

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corpus callosum

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deep groove in the cerebrum that divides the right and left hemispheres

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lobes

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each cerebrum hemisphere is divided into regions

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4 lobes of the hemispheres of the cerebrum

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frontal lobe, parietal lobe, occipital lobe, and temporal lobe

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cerebrum surfaces

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cerebral cortex and cerebral medulla

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cerebral cortex

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much of the cerebrum activity occurs here and it is composed of gray matter. The gray matter contains densely packed nerve cells

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cerebral medulla

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composed of white matter, which contains bundles of myelinated axons

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cerebellum

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2nd largest part of the brain and is located at the back of the skull. It controls balance, posture, and voluntary muscle contractions

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thalamus and hypothalamus

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found in the part of the brain between the brain stem and the cerebrum

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thalamus

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egg-shaped thalamus is the main site of sensory processing. Most of the sensory nerves converge on the thalamus

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hypothalamus

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below the thalamus. It is a slender thread of tissue that controls hunger, thirst, fatigue, anger, and body temperature. It also directs the secretions of the pituitary gland.

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brainstem

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connects the brain to the spinal cord and is composed of three parts. It coordinates and integrates all incoming information, while also serving as the place of entry or exit for 10 of the 12 cranial nerves. The lowest part of the brainstem is the medullaoblongata

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medulla oblongata

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controls involuntary functions that include breathing, blood pressure, heart rate, swallowing, and coughing.

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pons

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Just above the medulla oblongata, the brainstem enlarges to form the pons. This part provides a link between the cerebral cortex and the cerebellum. Above the pons is the smallest division of the brainstem

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midbrain

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Above the pons is the smallest division of the brainstem. It is involved in hearing and vision.

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spinal cord

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continuous with the brain and emerges from the opening at the base of the skull. It stretches downward for approximately 42 to 45 centimeters. It ends just below the ribs. Like the brain, it is protected by bone, meninges and cerebrospinal fluid. It carries impulses to and from the brain and regulates reflexes. Thirty-one pairs of spinal nerves originate in the spinal cord and branch out to the body.

Front 38

Coordination and balance occur principally in the

A spinal cord
B cerebellum
C cerebrum
D medulla oblongata

Back 38

The correct choice is B, because the cerebellum controls posture, balance, and voluntary muscle contractions. The spinal cord carries impulses to and from the brain and regulates reflexes. The cerebrum is responsible for all of the voluntary activities of the body. The medulla oblongata controls involuntary functions that include breathing, blood pressure, heart rate, swallowing, and coughing.

Front 39

2 divisons of peripheral nervous sytem

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sensory and motor

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sensory division

Back 40

transmits impulses from sense organs to the central nervous system

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motor division

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transmits impulses from the central nervous system to the muscles or glands.

Front 42

divisions of motor division

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somatic nervous system and autonomic nervous system

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somatic nervous system

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regulates activities that are under conscious control, such as moving skeletal muscles. However, many nerves within this system are reflexes that can act automatically. The receptor, sensory neuron, motor neuron, and effector that are involved in a reflex response are together known as a reflex arc.

Front 44

reflex arc

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receptor, sensory neuron, motor neuron, and effector that are involved in a reflex response are together

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autonomic nervous system

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the network that is used to maintain the body's homeostasis. By using it, the central nervous system regulates heart rate and controls muscle contractions in blood vessels, digestive, urinary, and reproductive tracts. It also carries messages to stimulate glands to secrete saliva, tears, and digestive enzymes.

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autonomic nervous sytem divisions

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sympathetic and parasympathetic nervous systems

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sympathetic division

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dominates in times of stress, such as "fight or flight" situations

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parasympathetic

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associated with "rest and digest" situations.

Front 49

The autonomic nervous system controls

A thinking
B digestion
C hearing
D walking

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B is the correct choice, because digestion is involved in homeostasis and the autonomic nervous system is what maintains the body's homeostasis. Thinking, hearing, and walking are not involved in homeostasis.

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ear

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distinguishes the pitch and loudness of sounds. also contain structures for detecting stimuli that make us aware of our movements and allow us to maintain balance.

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external ear

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fleshy part that helps to collect sounds and funnel them into the auditory canal

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auditory canal

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extends into the bones of the head but stops at the eardrum, or tympanum

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eardrum/tympanum

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the beginning of the middle. Sound waves strike it and cause it to to vibrate.

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3 middle ear bones

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hammer, anvil, and stirrup. transfer the vibration to a fluid-filled chamber within the inner ear

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cochlea

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a fluid-filled chamber within the inner ear. This chamber, which is shaped like a tightly coiled shell. When the fluid vibrates, tiny hair cells in this are pushed back and forth, providing stimulation that is turned into nerve impulses. These impulses travel on the auditory nerve to the brain

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semicircular canals

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The ears also contain structures for detecting stimuli that make us aware of our movements and allow us to maintain balance

Front 57

How many layers is each eye composed of?

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3

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outer layer of the eye

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consists of the sclera and cornea

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sclera

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consists of tough, white connective tissue. It helps maintain the eye's shape and provides a place of attachment for the eye muscles. In the front of the eye,

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cornea

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In the front of the eye, the sclera forms a transparent layer. Light will first pass through it, which will focus the light onto the back of the eye.

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middle layer of the eye

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consists of the choroid, ciliary body, and the iris

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choroid

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contains the blood vessels and becomes the disk-like iris

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iris

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gives the eye its color and controls the amount of light entering the eye

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pupil

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middle of iris is a small opening through which light will enter the eye

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lens

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Just behind the iris. Small muscles attached to it cause it to bend slightly. This bending enables the eye to focus on close and distant objects.

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inner layer of the eye

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retina

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retina

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the light-sensing portion of the eye. Special photoreceptors are arranged in a layer in this

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rods and cones

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generate nerve impulses, which travel up the optic nerve to the brain. In humans, the field of vision of the two eyes overlaps; each eye sees about one-third of what the other sees. In addition, the two eyes view an object from different angles.

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rods

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extremely sensitive to light and can detect various shades of gray even in dim light. They produce poorly defined images.

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cones

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detect color and are sensitive to edges, so they produce sharp images.

Front 71

The outer layer of the eye consists of the

A choroid, ciliary body, and iris
B cochlea
C retina
D sclera and cornea

Back 71

The correct choice is D, the sclera and cornea. Choice A is the middle layer and Choice C is the inner layer. Choice D is part of the ear.

Front 72

nose

Back 72

The sense of smell depends on receptors that detect specific chemicals in the environment. In the nose, the receptor cells are located in the upper part of the nasal cavity. These receptors contain cilia that extend into the air passageways of the nose and react to chemicals in the air. When they react to chemicals, the receptors are stimulated. This causes impulses to travel up the olfactory nerve to the brain.

Front 73

mouth

Back 73

The sense of taste is also a chemical sense. The organs that detect taste are the taste buds. About 10,000 taste buds are embedded within the surface of the tongue. Taste buds can also be located on the roof of the mouth and on the lips and throat. The taste buds detect four types of chemicals: sugars (sweet), acids (sour), alkaloids (bitter), and metal ions (salty). Generally, the tip of the tongue is sensitive to sweets, while the back of the tongue is sensitive to bitter. The sides of the tongue are sensitive to sour and salty. The taste buds are stimulated when a chemical dissolved in saliva binds to small hairs that protrude from the tip of the taste bud. This generates an impulse that travels to the brain.

Front 74

skin

Back 74

The sense of touch is not found in one particular place. All regions of the skin are sensitive to touch. There are several types of sensory receptors that lie just below the surface of the skin.

Two respond to heat and cold.
Two respond to touch.
One responds to pain.
Sensory receptors for heat and cold are usually scattered. Those for touch are more concentrated in some parts of the body than others. Pain receptors are located throughout the skin.

Front 75

The largest sense organ is the

A eye.
B nose.
C skin.
D ears.

Back 75

The correct choice is C. The skin has sensory receptors all over it. Choices A, B, and D are sense organs, but none of them are the largest.