Chapter 49: Chapter 49: Nervous Nervous SystemsSystems

By: Jordan Masterson

Difference Between Difference Between Invertebrates and Invertebrates and

VertebratesVertebratesInvertebrates Vertebrates

• Cnidarians are the simplest animals with nervous systems and radial symmetry. o Examples: Hydras and Jellyfish

• Series of interconnected nerve cells form a diffuse nerve net, a web like system of neurons.

• The Central Nervous System (CNS) consists of the brain and spinal cord.o Local dorsally (On The Back)

• The Peripheral Nervous System (PNS) transmits sensory and motor signals between the CNS and the rest of the body.

Comparison Comparison Figure 49.UN02Figure 49.UN02

Nerve net

Hydra (cnidarian) Salamander (vertebrate)

Sensoryganglia

Spinalcord(dorsalnervecord)

Brain

Figure 49.4Figure 49.4 Central nervoussystem (CNS)

Brain

Spinal cord

Peripheral nervoussystem (PNS)

Cranial nerves

Ganglia outsideCNS

Spinal nerves

Vertebrate Nervous SystemVertebrate Nervous System• The simplest circuits are found in the reflex

responses in which sensory input is linked to motor output without the involvement of the brain.o Example: a doctor using a mallet to trigger a knee-jerk reflex

Peripheral Nervous SystemPeripheral Nervous System• Afferent Neurons send information to the CNS.

o Example: Sensory Functions

• Efferent Neurons transmit information away from the CNS.o Example: Motor Functions and Automatic Nervous System

• Automatic Nervous System• Sympathetic Division: Activation corresponds to arousal and energy

generation (“Fight or Flight “).• Parasympathetic Division: Activation promotes calming and a

return to self-maintenance (“Rest and Digest”). • Enteric Division: Controls activity of the digestive tract, pancreas,

and gallbladder.

Parasympathetic division

Action on target organs:

Constricts pupilof eye

Stimulates salivarygland secretion

Constrictsbronchi in lungs

Slows heart

Stimulates activityof stomach and

intestines

Stimulates activityof pancreas

Stimulatesgallbladder

Promotes emptyingof bladder

Promotes erectionof genitalia

Cervical

Thoracic

Lumbar

SynapseSacral

Sympatheticganglia

Sympathetic division

Action on target organs:

Dilates pupil of eye

Accelerates heart

Inhibits salivarygland secretion

Relaxes bronchiin lungs

Inhibits activity ofstomach and intestines

Inhibits activityof pancreas

Stimulates glucoserelease from liver;inhibits gallbladder

Stimulatesadrenal medulla

Inhibits emptyingof bladder

Promotes ejaculationand vaginal contractions

Figure 49.8Figure 49.8

Regions of the BrainRegions of the BrainFigure 49.UN04Figure 49.UN04

Spinalcord

Cerebralcortex

Cerebellum

Medullaoblongata

Pons

Hindbrain

Midbrain

Forebrain

Cerebrum

Thalamus

Hypothalamus

Pituitary gland

The Vertebrate Brain is The Vertebrate Brain is Regionally Specialized Regionally Specialized

• The Brainstem: The Pons and Medulla serve as a relay station for information traveling between the PNS and higher brain.

• The Cerebellum: helps coordinate motor, perceptual, and cognitive functions.

• The Diencephalon: The Thalamus is the main center through which sensory and motor information passes to the cerebrum. The Hypothalamus regulates homeostasis and basic survival behaviors.

• The Cerebrum: has two hemispheres that are important in planning and learning movements. The Corpus Callosum provides communication between the right and left cerebral cortices.

The Cerebral CortexThe Cerebral Cortex• Four Lobes: frontal, temporal, occipital, and parietal• Information Processing in the Cerebral Cortex:

Adjacent association areas process particular in the sensory input and integrate information from different sensory areas.

• Language and Speech: Portions of the frontal and temporal lobes are essential for generating and understanding language.

• Lateralization and Cortical Function: The left cerebral hemisphere plays a dominant role in mathematics and logical operations. The right cerebral hemisphere mainly deals with pattern recognition and nonverbal thinking.

• Emotions: The experience of emotions involves many regions of the brain, with the amygdala playing a major role in generating emotions.

Changes in Changes in SynapticSynaptic

Connections Connections

Figure 49.19Figure 49.19

N2

N1

N2

N1

(a) Synapses are strengthened or weakened in response toactivity.

(b) If two synapses are often active at the same time, thestrength of the postsynaptic response may increase atboth synapses.

Nervous System DisordersNervous System Disorders• Schizophrenia: Characterized by hallucinations and

delusions, which affect neuronal pathways that use dopamine as a neurotransmitter.

• Depression: Patients that exhibit a persistent low mood are often treated with drugs that increase the activity of biogenic amines in the brain.

• Alzheimer’s: Age-related dementia where neurofibrillary tangles and amyloid plaques form on the brain.

• Parkinson’s: Motor disorder caused by the death of dopamine-secreting neurons with the presence of protein aggregates.

Drug Addiction Drug Addiction and Brain and Brain

Reward SystemReward System

Figure 49.23Figure 49.23 Nicotinestimulatesdopamine-releasingVTA neuron.

Inhibitory neuron

Dopamine-releasingVTA neuron

Cerebralneuron ofrewardpathway

Opium and heroindecrease activityof inhibitoryneuron.

Cocaine andamphetaminesblock removalof dopaminefrom synapticcleft.

Rewardsystemresponse