AP Psychology Ch 2 The Biological Perspective 1

AP Psychology Ch. 2 The Biological Perspective

1 Nervous System The nervous system is a network of cells that carries information to and from all parts of the body. Neuroscience deals with the neurons, nerves and nervous tissue that makeup the nervous system.

2 Nervous System (Cont’d) A neuron is a specialized cell that sends messages through the nervous system. Dendrites are parts of the neuron that receive messages from other cells. The cell body is called the soma The axon is like a tail, which sends messages to other cells.

3 Neurons make up approximately 10% of the brain. The remaining portion of the brain is made up of glial cells which serve as a foundation for the neurons to build on. Glial cells: Deliver neurons to neurons Clean up dead neurons Help process information Generate new neurons

4 Neurons (Cont’d) Neurons are separated by two types of glial cells. Oligodendrocytes – myelin in the central nervous system (brain & spinal cord) Schwann cells – myelin in the neurons of the body Bundles of myelin-coated cables form nerves.

5 - Neural Impulse When a cell is inactive it is called resting potential and it is filled with negative ions. When the axon send an electrical charge from positive ions it is called action potential. Axons contain short fibers called axon terminals with little saclike structures known as synaptic vesicles. Inside the synaptic vesicles lies neurotransmitters which transmit messages through a fluid-filled space called a synapse or synaptic gap.

6 - Neural Impulses (Cont’d) Drugs and toxins can have an effect on neural impulses. It depends on whether it was an excitatory or inhibitory signal. Agonists are chemical substances that enhance the effect of neurotransmitters. Antagonists are chemical substances that block or reduce a cell’s response.

7 Neural Impulses (cont’d) Acetylcholine gets released to control muscles. Curare is a drug that causes paralysis because it serves as an antagonist to block the release of acetylcholine. Venom from a black widow is an agonist because it enhances the release of acetylcholine leading to convulsions.

8 Reuptake and Enzymes Reuptake is the process by which the neurotransmitters get sucked back into the synaptic vesicles. Acetylcholine is a neurotransmitter to trigger muscle activity. An enzyme is a protein that is designed to break apart the acetylcholine so it clears the synaptic gap and doesn’t go through reuptake.

9 Reuptake and Enzymes (cont’d) Serotonin is a neurotransmitter that regulates people’s moods. Some people don’t produce enough serotonin to activate the receptors on the next neuron, leaving the person in a state of depression. People experiencing depression are often proscribed SSRI’s (selective serotonin reuptake inhibitors) which block reuptake so more serotonin can connect to the receptor site.

10 – Central Nervous System The brain and the spinal cord make up the central nervous system. The brain is the core of the central nervous system. The spinal cord is the highway where neurons send messages back and forth from the brain to the body.

11 – Reflex ARC The reflex ARC is the messages sent from the body to the brain and the reflex the brain sends back to the body. Reflexes are immediate without thinking about a response. 3 Neurons: Afferent (sensory) neurons – messages to the spinal cord Efferent (motor) neurons – messages from the spinal cord to the muscles Interneurons – connect other neurons and make up the spinal cord and the brain.

12 The Peripheral Nervous System (PNS) is the system of nerves and neurons outside of the Central Nervous System. The PNS can be divided into two systems: Somatic nervous system: comprised of the sensory pathway which consists of all of the nerves (afferent neurons) carrying messages to the CNS and the nerves carrying (efferent neurons) messages from the CNS to voluntary muscles. Autonomic nervous system: is the automatic nervous system in the body which controls organs, glands, involuntary muscles.

13 Autonomic Nervous System The autonomics nervous system is made up of two systems, the sympathetic division and the parasympathetic division. The sympathetic division is located by the spinal cord and controls our fight or flight system. This division would increase our heart rate, dilate our pupils and secrete adrenaline from the adrenal glands. The parasympathetic division controls the neurons at the top and bottom of the spinal cord and can be called the eat, drink and rest system. The parasympathetic division restores our body to normal.

14 Studying the Brain Testing on animals is done by stimulating or killing a portion of the brain. A wire with an electrical current is inserted into the brain of the animal to accomplish this. Then scientists study the effects. For humans, scientists obviously cannot intentionally cause brain damage. Instead they use a variety of tests to study the brain.

15 Testing the Brain Electroencephalograph (EEG) - this machine is designed to study the electrical activity of the neurons in the brain. This is accomplished by attaching metal discs to the patient’s head which send results to a computer. Think of it as an ultrasound for the brain. Scientists use EEG results to learn about sleep, seizures, tumors and the area of the brain being active.

16 Testing the Brain (Cont’d) CT scans (computed tomography) are like an x-ray of the brain. EEG’s only measure brain activity. CT scans can give scientists and doctors a look inside the brain. CT scans are used to determine stroke damage, tumors, injuries and other brain abnormalities.

17 Testing the Brain (Cont’d) MRI Scans (magnetic resonance imaging) is a machine that creates a magnetic field around the person placed inside it. The resulting image provides a 3 D image of the brain, which shows smaller details than a CT scan.

18 Testing the Brain (Cont’d) PET scans (positron emission tomography) provides a deeper look at the brain in action. Radioactive glucose is injected into the patient which projects an image of brain activity on a monitor. Patients are awake, so scientists can have them do different tasks to see which area of the brain is being used.

19 Testing the Brain (Cont’d) f. MRI (functional MRIs) are a method that tracks oxygen levels in the blood to determine which areas of the brain are active. f. MRI’s tend to be clearer than PET scans.

20 Structure of the Hindbrain Medulla – located at the top of the spinal cord and bottom of the brain. Controls breathing, heartbeat, and swallowing. This part of the brain sends and receives messages from all of the sensory nerves.

21 Hindbrain (Cont’d) The pons are next to the medulla and serve as a bridge between the different sections of the brain. The pons coordinate movement to each side of the body. The pons also influence sleep, dreaming and arousal.

22 Hindbrain (Cont’d) The Reticular Formation (RF) is a set of neurons running through the medulla and the pons. It’s function is to allow us to focus on certain things and alert us to changes in our surroundings. RF also keeps people alert and aroused. Studies on the RF of rats show that they wake up if their RF is stimulated. However if the rat’s RF is destroyed, they slip into a coma and never awaken.

23 Hindbrain (Cont’d) The cerebellum is at the base of the skull and sometimes referred to as the little brain. The cerebellum controls involuntary, fine motor movement. It also coordinates movement. A damaged cerebellum could result in being very uncoordinated, prone to dizziness and weakness and possibly slurred speech.

24 Structures Under the Cortex The cortex is the wrinkled outer layer of the brain packed with neurons and blood vessels. The limbic system is located in the upper brain and is involved in our emotions, motivation and learning. The limbic system includes the hypothalamus, hippocampus, and amygdala.

25 Under the Cortex (Cont’d) The thalamus processes the sensory information and relays it to the appropriate part of the brain. The hypothalamus regulates body temperature, thirst, hunger, sleeping and waking, sexual activity and emotions. The hippocampus deals with forming memories. Acetylcholine is a neurotransmitter that triggers muscle movement but also works with the hippocampus to develop memories.

26 Under the Cortex (Cont’d) The amygdala is responsible for fear responses and memory of fear. People and animals with damage to the amygdala are linked to a decreased fear response. 1939, monkeys with large amounts of their temporal lobes removed, were unafraid of snakes and humans. Rats with a damaged amygdala show no fear towards cats.

27 Lobes of the Cortex The cortex is divided into two cerebral hemispheres. The two hemispheres are connected by a band of neural fibers called the corpus callosum, which allows each side to communicate with the other. The occipital lobe is located in the rear base and processes information from the eyes. The parietal lobe is located at the top and back and processes information from the skin, temperature and balance. The Parietal lobe also contains the somatosensory cortex which receives info on touch and balance.

28 Lobes of the Cortex (Cont’d) The temporal lobes are located by the ear and temple and it processes auditory input. The frontal lobe is responsible for planning, personality, memory, decision making, language and controlling emotion. The frontal lobe also contains the motor cortex which controls voluntary muscles.

29 Endocrine Glands are organs that secrete chemicals from ducts, like saliva, tears, and sweat. Endocrine glands secrete hormones directly into the bloodstream. Some hormones released by the endocrine glands produce excitatory or inhibitory effects and thereby trigger an emotional reaction.

30 Endocrine Glands (cont’d) The pituitary gland is an organ in the brain near the hypothalamus that is referred to as the master gland because it controls all of the endocrine glands. The pituitary controls salt levels, triggers the production of breast milk and releases growth hormone.

31 Endocrine Glands (cont’d) The pineal gland secretes melatonin for the sleep-wake cycle. The thyroid secretes a hormone called thyroxin to regulate metabolism. The pancreas controls blood sugar and secretes insulin. The gonads include ovaries and testes which secrete hormones for sexual behavior and reproduction. The adrenal glands secrete corticoids which are steroids for the fight or flight reaction, along with cortisol to manage stress.