The Biological Basis for Behavior The Human Brain
Bellringer 3 • List at least five things your brain does on a daily basis.
I. Brain Basics • A. Studying the brain • 1. This area of the science of psychology is experiencing an explosion of research • 2. This is mostly due to changes in technology that allow us to see the brain as it works.
B. Phrenology • 1. A concept developed by a German Physician named Franz Gall in the early 1800’s. • 2. The theory stated that bumps on the skull revealed our mental abilities and personality traits. Phrenology
C. Basic Terminology • 1. Biological psychologist = a branch of psychology concerned with the links between biology and behavior. • 2. Sometimes referred to as neuropsychology, neuroscience, physiological psychology, or biopsychology. • 3. Neuroanatomy refers to the study of the parts and functions of neurons
II. Neural anatomy and Neural Communication • A. Neurons the basic building blocks of the brain • electrically transmit data in your brain • makeup 1/2 the volume of the brain Neurons
B. Glial Cells support the neurons • 1. May be 10 times as numerous as neurons • 2. Make up the other half of the volume of the brain • surround neurons and hold them in place • supply nutrients and oxygen to neurons • insulate one neuron from another • destroy pathogens and remove dead neurons.
C. Neurons • 1. Three types of Neurons • a. Sensory = neurons that carry incoming information from the sense receptors to the central nervous system. Sensory Neuron
Brain Sensory Neuron Spinal Cord Motor Neuron Neurons Continued… • b. Motor = the neurons that carry outgoing messages from the CNS to the muscles and glands. • c. Interneurons = CNS neurons that internally communicate and intervene between the sensory inputs and motor outputs • Nervous system consists of billions and billions (A LOT more than sensory & motor neurons)
2. The structure of the Neuron • a. Dendrites = the bushy, branching extensions of a neuron that receive messages and conduct impulses forward toward the cell body. • b. Axon = the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands • c. The Soma = the Cell body – its function is to support the cell. At the center is the nucleus
d. The myelin sheath is a layer of fatty segmented tissue that encases the fibers of many neurons • Enables vastly greater transmission speed of neural impulses as the impulse hops from one node (link) to the next • Degeneration leads to multiple sclerosis • e. The Synapse (synaptic gap)= the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron
f. The axon terminal = is the bulb at the end of an axon through which neurotransmitters are released. • g. Vesicles = bubble like structures which contain the neurotransmitters
3. The Neuron at Rest • a. Resting potential = the interior cellular fluid of the axon has a slightly higher negative charge. This positive outside/negative inside polarization is called resting potential • b. The cell membrane is selectively permeable • Only allows certain ions in or out
c. Example: Sodium & Potassium pump = the resting cell continually pumps three sodium ions out while letting two potassium ions in – Since both of these ions have a positive charge the result is a slight decrease in the positive charge of the inside of the cell Outside of Cell Na+ Na+ Na+ Cell Membrane in resting state K+ K+ Inside of Cell
4. The Action Potential • a. Action potential = a neural impulse • i. A brief electrical charge that travels down an axon • ii. The action potential is generated by the movement of positively charged sodium ions into the axon- this depolarizes the affected sections of the axon • This happens 100 – 1000 times per…SECOND!
Each neuron is a mini decision making device, receiving signals. • Some signals call for neuron’s acceleration- Some signals call for the brake! • If a push for more acceleration occurs, exceeding the threshold happens. • b. Thresholds = the level of stimulation required to trigger a neural impulse • c. The all-or-none law • Neurons are like guns (they either fire or don’t fire) • The size, amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it • How do we detect a gentle touch from a big hug? • Neurons don’t fire faster instead more neurons are fired and fired more often.
Resting Potential • At rest the inside of the cell is at -70 microvolts • If resting potential rises above threshold an action potential starts to travel from cell body down the axon • This shows resting axon being approached by an AP
Depolarization ahead of AP • AP opens cell membrane to allow sodium (NA+) in • Inside of cell rapidly becomes more positive than outside • This depolarization travels down the axon as leading edge of the AP
Repolarization follows • After depolarization potassium (K+) moves out restoring the inside to a negative voltage • This is called repolarization • The rapid depolarization and repolarization produce a pattern called a spike discharge
d. The refractory period is the time during which a neuron resists further action potentials while it recharges
Bell Ringer 4 • How is a neuron firing like a toilet flushing? Be sure to include the following vocabulary in your explanation (underline each term). • Resting Potential • Threshold • Action Potential • All or none • Depolarization • Refractory Period
Outside of Cell K+ Na+ Cl- Cell Membrane in resting state K+ Na+ Cl- A- Inside of Cell Ion concentrations
K+ Na+ Cl- Outside of Cell Cell Membrane at rest Na+ - 70 mv A- K+ Cl- Inside of Cell Potassium (K+) can pass through to equalize its concentration Sodium and Chlorine cannot pass through Result - inside is negative relative to outside The Cell Membrane is Semi-Permeable
Neurotransmitters • Neurotransmitters = chemical messengers that cross the synaptic gaps between neurons. • Create or inhibit the receiving neuron from generating a neural impulse • Synaptic receptor sites – AKA binding sites – each site is like a lock keyed to the particular chemical structure of each different type of neurotransmitter
Endorphins • a. Natural pain killers in the brain (the body’s natural opiate) • A person runs for a long period of time and after pushing through the wall, endorphins are released into the body to produce a feeling of euphoria in the runner’s body • This is what is call a runner’s high • b. Morphine is a synthetic endorphin • An agonist which mimics Usain Bolt- Fastest Man On Earth. 100 meters/328 feet in 9.58 seconds
Say NO to Drugs because… • Drugs and other chemicals alter neurotransmission • 1. Agonist work by mimicking a particular neurotransmitter or by blocking its reuptake (or absorption back into the body) • 2. Antagonist work by blocking the release of particular neurotransmitters. • 3. Artificial opiates can cause the brain to stop producing endorphins which leads to INTENSE DISCOMFORT!
Task • Turn to page 57 in your book. • Copy Table 3A.1 (Some Neurotransmitters & Their Functions)
III. Neurotransmitters • A. Serotonin • 1. Affects mood, hunger, sleep and arousal • 2. Implicated in states of consciousness • 3. Prozac and similar antidepressant drugs raise serotonin levels • 4. LSD seems to act on this system Serotonin
c. Substance P is a neuro-cheimical that is still not fully understood but researchers suspect that it is involved in triggering the pain response
B. Dopamine • 1. Influences movement, learning, attention and emotion • 2. Excess activity at dopamine receptor sites is associated with schizophrenia • 3. Too little activity is associated with Parkinson’s • C. Norepinephrine • 1. Helps control alertness and arousal • 2. Too little can lead to depression • 3. Too much can lead to manic episodes Dopamine & Drugs Norepinephrine
D. Acetycholine • 1. Works on neurons involved in muscle action, learning and memory • 2. The poison curare works by blocking ACh • 3. Patients with Alzheimer’s show a deterioration in this chemical messenger • E. GABA = gamma aminobutyric acid • 1. Serves inhibitory functions and is sometimes implicated in eating and sleeping disorders • 2. Also implicated in anxiety • 3. Works with valium by increasing GABA which decreases anxiety.
F. Glutamate • 1. Is the main excitatory neurotransmitter in the brain • 2. Some people have an adverse reaction to MSG (Monosodium Glutamate) in Chinese food, it tends to wind them up and make them feel anxious
How the Nervous System Works… • The nervous system is always active and never rests • Even when you are sleeping the nervous system is regulating your body functions • The nervous system is divided into two parts: • Central Nervous System (CNS) • Peripheral Nervous System (PNS)
The Central Nervous System • It consist of the brain and the spinal • cord • Cerebrospinal Fluid (CFS) is a liquid similar to blood serum found in the ventricles of the brain and in the central canal of the spinal cord • The Blood-Brain Barrier is the mechanism that keeps many chemicals from crossing from the blood stream into the brain. This keeps most viruses out of our brain. Certain chemicals like drugs are dissolved in fats and can cross the barrier.
The Peripheral Nervous System PNS • These are nerves branching beyond the spinal cord into the body • Sensory and motor neurons that connect the CNS to the rest of the body • It sends sensory input to the brain and relays commands from the brain to muscles • Its job is to contact the bodies organs and relay the messages back to spinal cord
Neurons are the nervous system’s building blocks • PNS info travels through axons that are bundled into the electrical cables we know as nerves. • This connects the CNS with muscles, glands, and sense organs
The PNS consists of… • The Somatic System = the division of the PNS that controls the body’s skeletal muscles (skeletal nervous system) • Biceps, quads, triceps, etc • Autonomic System = the part of the PNS that controls the glands and the muscles of internal organs. • Heart, liver, kidneys, etc.
Autonomic Nervous System Cont… • Sympathetic Nervous System = the division of the ANS that arouses the body & mobilizes its energy in stressful situations • Parasympathetic Nervous System = the division of the ANS that calms the body, conserving its energy
Sympathetic Nervous System Dilates pupils Accelerates heartbeat Inhibits digestion Stimulates release of adrenaline, Releases the bladder Parasympathetic Nervous System Contracts pupils Slows heartbeat Stimulates digestion Contracts bladder The Autonomic Nervous System