Biology

1
Biology
2
The Nervous System

• Two main parts
• Central Nervous System
• Consists of the brain and spinal cord
• Peripheral Nervous System
• Consists of nerve cells that send messages
  between the central nervous system and all the
  parts of the body

3
Neurons

• Neurons- nerve cells
• Send and receive messages from other structures
  in the body such as muscles and glands

4
Neurons

• Components of a neuron
• Cell Body- produces energy that fuels the
  activity of the cell
• Dendrites- thin fibers which branch out of the
  cell, receive information from other neurons and
  pass the message through the cell body
• Axon- carries messages away from the neuron,
  single fiber
• Myelin- covering of the axon, insulates and
  protects the axon, helps to speed up the
  transmission of the message
• Axon terminal- small fibers branching out from an
  axon

5
Types of Neurons

• Sensory- carry messages from sense organs to
  spinal cord or brain
• Motor- carry messages from spinal cord or brain
  to muscles or glands
• Interneurons- carry messages from one neuron to
  another and do most of the work of the nervous
  system

6
How do Neurons communicate?

• Neurons send messages across synapses through the
  release of neurotransmitters
• Chemicals that are stored in sacs in the axon
  terminal

7
Nerve Impulses

• Absolute refractory period- after one cell
  firing, it will not fire again regardless of how
  strong the incoming message is
• Relative refractory period- time when neuron is
  returning to normal and may refire if message is
  stronger then usual
• All or none law- a neuron fires at full capacity
  or does not fire at all

8
Firing of a nerve cell

• Dendrite or cell body picks up message
• If message is strong enough, neuron fires and
  impulse starts down the axon
• Out the end of the axon terminal to the synaptic
  knob
• On to the next nerve cell

9
Central Nervous System

• 2 major parts
• Central Nervous System- brain and spinal cord
• Peripheral Nervous System- connects brain, spinal
  cord to every other part of the body

10
Brain

• Areas of the Brain
• Hindbrain- co-ordinate motor activity, posture,
  equilibrium, sleep patterns, and regulate
  unconscious functions (ex. blood circulation and
  breathing)
• Midbrain- vision, hearing, motor control,
  sleep/awake cycle, arousal (alertness), and
  temperature regulation
• Forebrain- controls cognitive, sensory, and motor
  functions, regulate body temperature,
  reproductive functions, eating, sleeping, and
  display of emotions

11
Brain

• Parts of the Brain
• Amygdala- storing classifying emotional
  memories, produces emotions
• Hippocampus- memory formation, classifying
  information, long-term memory
• Thalamus- sensory signals, visual information,
  information from skin and internal organs, motor
  control
• Hypothalamus- metabolic processes, body
  temperature, hunger, thirst, fatigue, anger, and
  circadian cycles

12
Brain

• Cerebellum- regulates coordinates movement,
  posture, and balance
• Pons- relays messages to other parts of the
  brain, controls arousal, and respiration
• Medulla Oblongata- heart rate, respiration, blood
  pressure, swallowing, vomiting, and defecation,
  relay station for nerve signals going to/from the
  brain

13
Brain

• Lobes of the Brain
• Occipital- receives and interprets visual
  information
• Temporal- controls hearing and some processing of
  visual and olfactory information
• Parietal- responds to sensations of touch bodily
  position
• Frontal- responsible for voluntary movement-
  attention, goal-directed behavior, and
  appropriate emotional experiences

14
Brain

• Hemispheres
• Left- right-hand touch and movement, speech,
  language, and writing
• Right- left-hand touch and movement, spatial
  construction, non-verbal imagery, and face
  recognition

15
Peripheral Nervous System

• Carries messages to and from the Central Nervous
  System
• Made of two major parts
• Somatic Nervous System
• Autonomic Nervous System

16
Somatic Nervous System

• Composed of all sensory (afferent) neurons that
  carry information to the CNS and all the motor
  (efferent) neurons that carry messages from the
  CNS to the skeletal muscles of the body
• The senses have their origin in the somatic part
  of the Peripheral Nervous System

17
Autonomic Nervous System

• Composed of all the neurons that carry messages
  between the CNS and all the internal organs of
  the body (glands and smooth muscles such as the
  heart and digestive system)
• Important in breathing, blood flow, and emotions
• Has two branches- sympathetic and parasympathetic
• Both are involved in controlling and integrating
  actions of the glands and smooth muscles

18
Sympathetic and Parasympathetic Nervous Systems

• Sympathetic
• Tell the body to prepare for an emergency
• Heart pounds, breathe faster, pupils enlarge,
  digestion stops
• Tells the endocrine system to release chemicals
  into bloodstream
• Connect to every internal organ of body

• Parasympathetic
• Calms the body down after stress

19
The Endocrine System

• Consists of glands which secrete hormones into
  the bloodstream
• Hormones- stimulate growth and affect behavior
  and emotional reactions
• produced by different glands- pituitary, thyroid,
  adrenal, testes, and ovaries

20
Pituitary Gland

• Lies below the hypothalamus
• Considered the Master Gland
• Secretes different hormones
• Growth- regulates growth of muscles, bones, and
  glands
• Prolactin- stimulates production of milk in
  nursing women
• Oxytocin- stimulates labor in pregnant women

21
Thyroid Gland

• Produces thyroxin
• Affects the bodys metabolism- the rate of
  converting food to energy
• Low production can lead to hypothyroidism- can
  cause people to be overweight
• High production can lead to hyperthyroidism- can
  cause excitability, inability to sleep, and
  weight loss

22
Adrenal Gland

• Located above the kidneys
• Secretes cortical steroids- increase the
  resistance to stress and promote muscle
  development, can cause the liver to release
  stored sugar in emergencies
• Produce adrenaline and noradrenaline
• Arouse the body for an emergency
• Adrenaline- can intensify emotions (fear
  anxiety)
• Noradrenaline- raises blood pressure

23
Testes and Ovaries

• Testes- males
• Ovaries- females
• Each produces hormones- testosterone, estrogen,
  and progesterone

24
Testosterone

• Testosterone- male sex hormone, small amount
  found in females
• Influences the development of sex organs (if
  secreted child will be male, if not- female)
• Aids in growth of muscle and bone, primary and
  secondary sex characteristics
• Primary sex characteristics- directly involved in
  reproduction
• Secondary sex characteristics- distinguish males
  from females

25
Estrogen Progesterone

• Female sex hormones but small amounts are found
  in males
• Females- ovaries produce estrogen and
  progesterone
• Males- testes produce estrogen and progesterone

26
Estrogen Progesterone

• Estrogen-Development of primary and secondary sex
  characteristics
• Progesterone- stimulates growth of female
  reproductive organs and prepares the body for
  pregnancy
• Both regulate menstrual cycle and vary during the
  cycle
• Changing levels of estrogen are linked to PMS
• Estrogen is connected to cognitive functioning
  and feelings of well-being among women