Download The Nervous System and Senses

The Nervous System and Endocrine
System
Compare and contrast
• Both transmit signals to other areas of the body
• Nervous system
• Very rapid
• Uses neurons to relay electrical and chemical signals
• Controls all of the body (everything that the body does)
• Endocrine System
• Slower
• Uses glands and hormones secreted into the blood vessels
• Controls certain bodily functions (growth, metabolism, sexual development,
use of minerals and other substances)
The Nervous System
• Group of organs that controls the body
• Thought, movement, and all life processes
• Responds to external stimuli
• Information gathered through the senses
• Stimulus-something that causes a response
• Very fast
• Information can pass in less than a second
• 2 parts:
• Central Nervous System
• Brain and spinal cord
• Peripheral Nervous System
• Rest of the body
Neurons
• Cells of the nervous system
• 3 main parts:
• Cell Body
• Contains the nucleus and organelles
• Dendrite
• Receive information from neighboring cells
• Axon
• Transmits information to other cells
• 3 Types of Neurons:
• Sensory neurons-Gather information
• Interneurons- Receive and relay information to and from CNS
• Motor neurons-Pass information from CNS to tissues
Transmission of Information
• Uses a concentration difference of ions
(charged atoms) to create electrical
signals through the neuron
• Synapse
• Area between neurons
• Information leaves one neuron through the
axon and crosses a synapse to the dendrite
of another neuron
• The information is in the form of chemical
signals called neurotransmitters
The Senses
• The only way to gather information about your surroundings
• Maintain homeostasis
• Shiver when cold, sweat when hot, eyes dilate in dim lighting, etc.
• 5 senses:
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Sight
Hearing
Smell
Taste
Touch
Vision
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Most used sense for humans
The eye is the sensory organ
Contains photoreceptors (rods and cones)
Uses reflected light
• The eye is covered with a protective layer called the cornea
• Muscles around the iris (the colored portion) control the size of the pupil
(the black circle), controlling how much light enters the eye
• From the pupil, light passes through a lens, which focuses light on the back of
the eye (retina)
• Rods and cones on the retina generate nerve impulses that travel through the optic
nerve to the brain
Vision Problems
• Nearsightedness (myopia)
• Eyes focus on close objects, but not on far away ones
• Light is focused in front of the retina
• Farsightedness (hyperopia)
• Eyes focus on far objects, but not close ones
• Light is focused behind the retina
• Astigmatism
• Irregular curvature of the eye
• Scatters light so that it hits multiple areas on the retina
• All are easily corrected with lenses (glasses and contacts)
Hearing
• The ear is the sensory organ
• Contains auditory receptors called hair cells
• Ear has 3 parts:
• Outer ear
• Part we see is called the pinna
• Pinna collects sound waves and focuses them into the auditory canal
• At end of the auditory canal is the tympanic membrane (eardrum), which vibrates
• Middle ear
• 3 bones (malleus, incus, stapes) are vibrated by Tympanic membrane and
amplify sound
• Inner ear
• Amplified sound enters fluid-filled cochlea, which contain hair cells
• The hair cells bend as fluid moves, creating nerve impulses
• Impulses travel through auditory nerve to brain
The ear and balance
• The semicircular canals (part of the
cochlea) are also filled with fluid
• As you move, the fluid moves and
stimulates hair cells in the semicircular
canals
• They transmit impulses to the brain, which
interprets them and orients your body
Smell and Taste
• Closely related senses
• Each have chemoreceptors that detect molecules
• The ones on your tongue are called taste buds
• The chemoreceptors generate impulses that pass through nerves to the
brain
Touch
• Sensed in the epidermis and
dermis of the skin
• Mechanoreceptors
• Some are sensitive to light tough
• Some are sensitive to pain
• Some are only sensitive to deep
touch
• Some are wrapped around hair
follicles and sense hair
movement
The Brain and Spinal Cord
• Part of the CNS
• Made up of neurons orientated in a pattern
• Dense portions of cell bodies are called gray matter
• Dense portions of axons are called white matter
• In the brain, gray matter is on the outside
• In the spinal cord, gray matter is on the inside
• 3 layers of tissue protect the brain
• Called meninges
• If this becomes inflamed, it is meningitis
• Brain divided into 3 main parts
Cerebrum
• Largest portion
• Interprets signals from the body
• Emotion, needs, motion, pain
• 2 hemispheres connected by nerves
• Each controls the opposite side of the body
• The thick band of nerves connecting the hemispheres is called the corpus callosum
• Outer layer of the cerebrum is the cerebral cortex (folded portion)
• Areas of the cerebral cortex that do a task are called lobes
• 4 main lobes
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Frontal: Planning, personality, reasoning, judgement, voluntary motion, speech (Broca’s area)
Parietal: Touch and language processing
Occipital: Vision
Temporal: Speech interpretation, hearing, memory
Cerebellum
• Coordinates movement
• Maintain posture and balance
• Muscle memory
Brain Stem
• Connects brain to spinal cord
• Controls involuntary actions
• Reflexes
Spinal Cord
• Connects brain to rest of body
• Delivers messages to muscles
• Damage to spinal cord can lead to paralysis
• Disconnects neurons from the brain
• Reflexes pass to the spinal cord, then back to
the muscle
• Does not need to travel through the brain, so quicker
Peripheral Nervous System
• Connect CNS to rest of body
• 2 parts:
• Somatic Nervous System
• Controls voluntary movement
• Autonomic Nervous System
• Controls involuntary movement
• 2 parts:
• Sympathetic Nervous System-”fight or flight” response
• Parasympathetic Nervous System-calms body
Important Neurotransmitters
• Dopamine-Role in emotion, stress, and voluntary muscle
movement
• Serotonin-Role in emotion, muscle, and hunger
• Homeostasis is maintained if the levels are correct
• Incorrect levels of dopamine affect muscles
• Can lead to Parkinson’s Disease and Schizophrenia
• Incorrect levels of serotonin can lead to anxiety and depression
Drugs and the Brain
• Drugs alter the release of neurotransmitters
• Can train your body to depend on them
• Called addiction
• When the drug is stopped, the body senses something is wrong and leads to
the effects of withdrawal
• Stimulants increase the release of neurotransmitters
• Depressants reduce the release of neurotransmitters, or block the
receptors
The Endocrine System
• Group of glands that release
chemical messages into the
blood
• Called hormones
• 2 categories of hormones
• Steroid hormones
• Attach to DNA
• Nonsteroidal hormones
• Chemical reaction in
cytoplasm
• Attach to target cells
Main Endocrine Glands
• Hypothalamus
• Found in brain
• Causes release of growth hormones and control the reproductive system
• Controls the pituitary gland
• Pituitary Gland
• Also found in brain
• Releases growth hormone and causes blood to absorb water from the
kidneys
• Also controls function of other glands
More Endocrine Glands
• Thyroid
• In throat
• Controls metabolism
• Parathyroid
• On thyroid
• Controls how the body uses calcium
• Thymus
• In chest
• Causes WBCs to mature and reproduce
• Adrenal Glands
• In torso above kidneys
• Help respond to stress (“fight or flight”)
Last of the Endocrine Glands
• Pancreas
• Between stomach and intestines
• Controls the use of glucose
• Produces insulin
• Gonads
• Ovaries in females and testes in males
• Estrogen in females and testosterone in males
• Release sex hormones, controls production of gametes, development of sex
characteristics
Feedback Loops
• Positive Feedback
• The production of a hormone causes more to be released
• Not as common
• Childbirth
• Negative Feedback
• The production of the hormone stops hormone release
• Most common in body